That way speciation syndrome may not be so uncanny afterall.
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Instead of slowing down, the kiwi's speciation rates increased fivefold.
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Our work has shown that this model of speciation does hold.
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Those are absolute world records in terms of speed of speciation.
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How has our understanding of speciation—the development of new species—changed?
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RG: The [traditional] model of speciation was almost a three-step process.
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To answer that question, let's first look at speciation syndrome's cousin concept.
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At some point, the lines of extinction and speciation will cross again.
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Is this a speciation moment, or are they just things to be owned?
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Why this matters: Speciation occurs when individuals from two groups no longer breed.
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Since diet influences habitat and behavior, changes in beak shape could trigger speciation.
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"It contributes to an ongoing debate right now," on what factors are driving speciation.
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The researchers believe that hybridization could be a key driver of speciation and biodiversity.
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One of the most famous examples of recent speciation involves the cichlid fishes of Africa's Lake Malawi.
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A recent study found that birdsong is genetic in flycatchers , and could be a mechanism for speciation.
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Instead, Dr. Janke said, at least some of the whale speciation has been driven by personal taste.
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"The biological processes of evolutionary divergence and speciation have not been broken in the Anthropocene," Thomas writes.
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This relatively new—and deceptively catastrophic—adaptation, called "human-mediated speciation," was explored in a study published this week in the Proceedings of the Royal Society B. When a plant, animal, or bacteria undergoes "speciation," its evolutionary lineage will split off into two or more unique gene pools.
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Adaptation and speciation are ongoing processes that are happening in lineages all over the planet all the time.
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But still, on each of the Channel Islands the foxes were undergoing the long, slow process of speciation.
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I call this unease speciation syndrome, where witnessing significant physical genetic transformation of human beings causes revulsion and shock.
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You need to break continents and continental shelves apart, and separate one ocean from another, for speciation to occur.
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One way such speciation might happen is when two geographically separate populations that are derived from a single species meet.
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According to Baco-Taylor, they're regions of high biodiversity, and their relative isolation makes them an important place for speciation.
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But in addition, we have shown there are other routes to speciation, such as gene flow from one species to another.
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PG: Our understanding of evolution in general and speciation in particular is undergoing a large transformation as a result of genomics.
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But of course, first we must get over our fears of modifying the human body and the effects of speciation syndrome.
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Over the Triassic and Jurassic, dinosaur diversity was on the rise, but by the early Cretaceous, speciation had begun to plateau.
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What we do know, as evolutionary biologists, is that there are intrinsic features of organisms that increase their likelihood of rapid speciation.
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These go beyond the fact that speciation tends to be a much more gradual process than it's often made out to be.
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"Those cave bear genes that are never found in brown bears (as incompatible) might prove essential to understand the process of speciation," he said.
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What they discovered was resounding evidence for human-mediated speciation because of habitat disruption, invasive species, domestication, hunting, and hybridization (think: "pizzlies" and "grolar bears").
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My wife studies fly speciation and her work focuses on recent divergences in flies that feed on different kinds of holly trees in the eastern United States.
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Speciation is ongoing, and species that are in the process of forming will only become unambiguously separate after longer time has elapsed than we can observe directly.
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If we're too closed-minded about such radical science, we might find ourselves embroiled in a state of hostile speciation, where another new cold war swallows a generation.
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All around the world there is similar evidence of hybridisation and incipient speciation as separated populations go their different ways and get it on with different far-flung relatives.
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They spoke of speciation as a "gradual process," and mused on the difficulty of distinguishing between, say, an adaptively tricked-out Anolis lizard and an entirely new kind of reptile.
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In addition, we often see the highest rates of speciation and divergence among groups of organisms that have evolved key evolutionary innovations that allow them to colonize previously unexploited ecological niches.
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One of the most obvious drivers of speciation is the destruction of ecosystems by the combined forces of climate change, natural resource extraction, development, and the introduction of harmful invasive species.
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This is in contrast to cladogenesis, which Carr calls "the default hypothesis for speciation," in which a daughter species branches off from a parent lineage, but both species still synchronously exist.
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I surmise with speciation syndrome humanity will also discover its sense of limits to what genetic editing means for future human form—and this discovery will probably ultimately cause revulsion at first.
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The idea that today's decimation is qualitatively different to the mass extinctions of yore, and that a compensating mass speciation is already under way, seems at some level to be quite encouraging.
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The research, outlined in the journal Proceedings of the National Academy of Sciences, is the first to incorporate phylogenetic information — meaning how species are related to one another — when studying speciation and extinction in dinosaurs.
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One could argue, however, that the coming Star Wars-like age of speciation—as widely seen in a rough bar on planet Tatooine—will challenge our mental outlook on the human form far more than machines.
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Given enough time, and assuming Britons don't alter their bird feeding habits, this could eventually result in the emergence of an entirely new subspecies of great tit, an evolutionary process that biologists refer to as speciation.
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The new Luzon evidence "might be mimicking what we know now on Flores Island, meaning an early colonization of an isolated island followed by the diminution in body size and speciation of this remote hominin population," Ingicco said.
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While he found the study interesting, Paul Wignall from the University of Leeds told Gizmodo that he'd like to see followup studies of climate and environmental changes during this period that could have resulted in speciation and extinction events.
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It's too soon to say how frequently mitonuclear conflict acts as a force in speciation, but researchers agree that better understanding of that tension may help to solve mysteries about what barricade separates some apparently similar populations into distinct species.
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As the geneticist Sarah Tishkoff of the University of Pennsylvania reminded me, human beings are too young as a species, too promiscuous and full of wanderlust, always moving and mixing, for the kind of separation and differentiation that would cause true speciation to have occurred.
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That is, we see the same changes in the same set of genetic loci (both those that code for proteins and those loci that regulate the expression of those genes) each time there is a speciation event, from the marine ancestors to the newly evolved freshwater descendant species!
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The question of which animal species formed most recently is quite hard to answer because the process of divergence into separate species—called speciation—takes place over long time periods and therefore it is hard to categorically say at what point there is a transition from "two populations of the same species" to "two species".
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Leif AnderssonProfessor, Genomics, Uppsala University, and the one of world's most renowned scholars in the genomic and molecular study of domestic animalsThis is a question that has no answer for two major reasons: Speciation is a gradual process, and there is no real sharp border where two populations have diverged to the extent that they are two distinct species.
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After lots of number crunching and analysis, the divergence dates of the major groups separated by continents seemed to line up well with the continents separating geographically, according to the paper published this week in the Proceedings of the Royal Society B. This adds further evidence to the importance of vicariance, over dispersal, as the cause for further speciation.
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Axel MeyerProfessor, Biology, University of Konstanz, best known for his work on the role of ecological and sexual selection in speciation, among other thingsIn Lake Victoria, more than 0003 new endemic species of fish originated in less than 15,000 years, and in some of the crater lakes in Nicaragua that are less than 2000 years old, we find endemic species that we've estimated to be only a few hundred generations old.
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Fact Sheet. USFWS. It is thought to have evolved outside the usual model of allopatric speciation, from its parental species Stephanomeria exigua. As such this plant is one of the best plant examples of "quantum speciation," a concept closely aligned with peripatric speciation, parapatric speciation and sympatric speciation.
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These may drive allopatric speciation, which is arguably the dominant mode of speciation.
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The botanists G. Ledyard Stebbins and Verne Grant were two of the well known botanists who championed the idea of hybrid speciation during the 1950s to the 1980s. Hybrid speciation, also called polyploid speciation (or polyploidy) is speciation that results by an increase in the number of sets of chromosomes. It is effectively a form of sympatric speciation that happens instantly. Grant coined the term recombinational speciation in 1981; a special form of hybrid speciation where a new species results from hybridization and is itself, reproductively isolated from both its parents.
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It grows in chaparral, oak woodlands, and yellow pine forest habitats. As the putative progenitor species of Clarkia lingulata it is often used in examples of evolution outside the usual model of allopatric speciation. As such this plant is one of the best plant examples when considering "quantum speciation," a concept closely aligned with peripatric speciation, parapatric speciation and sympatric speciation.
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Various alternative models have been developed concerning allopatric speciation. Special cases of vicariant speciation have been studied in great detail, one of which is peripatric speciation, whereby a small subset of a species population becomes isolated geographically; and centrifugal speciation, an alternative model of peripatric speciation concerning expansion and contraction of a species' range. Other minor allopatric models have also been developed are discussed below.
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Since then, research on speciation has expanded immensely. The language of speciation has grown more complex. Debate over classification schemes on the mechanisms of speciation and reproductive isolation continue. The 21st century has seen a resurgence in the study of speciation, with new techniques such as molecular phylogenetics and systematics.
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Once again, take note of the established fact that, "...natural selection is a ubiquitous part of speciation...", and is the primary driver of speciation, so; hereinafter, examples of speciation will often interdepend and correspond with selection.
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Sympatric speciation, from its beginnings with Darwin (who did not coin the term), has been a contentious issue. Mayr, along with many other evolutionary biologists, interpreted Darwins's view of speciation and the origin of biodiversity as arising by species entering new ecological niches—a form of sympatric speciation. Before Mayr, sympatric speciation was regarded as the primary mode of speciation. In 1963, Mayr provided a strong criticism, citing various flaws in the theory.
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Coyne and Orr in Speciation categorise these forms into three groups: clinal (environmental gradients), "stepping-stone" (discrete populations), and stasipatric speciation in concordance with most of the parapatric speciation literature. Henceforth, the models are subdivided following a similar format. Charles Darwin was the first to propose this mode of speciation. It was not until 1930 when Ronald Fisher published The Genetical Theory of Natural Selection where he outlined a verbal theoretical model of clinal speciation.
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Allopatric speciation is where new gene pools arise out of natural selection in isolated gene pools. Island biogeography is also useful in considering sympatric speciation, the idea of different species arising from one ancestral species in the same area. Interbreeding between the two differently adapted species would prevent speciation, but in some species, sympatric speciation appears to have occurred.
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Further concepts developed by Barton and Hewitt in studying 170 hybrid zones, suggested that parapatric speciation can result from the same components that cause allopatric speciation. Called para- allopatric speciation, populations begin diverging parapatrically, fully speciating only after allopatry.
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These new conditions directly drove the speciation of the Tillandsioides, and also drove the speciation of their animal pollinators, such as hummingbirds.
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European Holly (Ilex aquifolium). The genus Ilex is an example of ecological speciation. Gasterosteus aculeatus, a documented case of ecological speciation Centaurea solstitialis, a candidate species for ecological speciation Ecological speciation is the process by which ecologically based divergent selection between different environments leads to the creation of reproductive barriers between populations. This is often the result of selection over traits which are genetically correlated to reproductive isolation, thus speciation occurs as a by-product of adaptive divergence.
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The late 20th century saw the development of mathematical models of allopatric speciation, leading to the clear theoretical plausibility that geographic isolation can result in the reproductive isolation of two populations. Since the 1940s, allopatric speciation has been accepted. Today, it is widely regarded as the most common form of speciation taking place in nature. However, this is not without controversy, as both parapatric and sympatric speciation are both considered tenable modes of speciation that occur in nature.
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The results suggested a "strong confirmation of the ecological speciation hypothesis" and amply supported parallel speciation taking place within the different blue holes.
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It is widely thought that parapatric speciation is far more common in oceanic species due to the low probability of the presence of full geographic barriers (required in allopatry). Numerous studies conducted have documented parapatric speciation in marine organisms. Bernd Kramer and colleagues found evidence of parapatric speciation in Mormyrid fish (Pollimyrus castelnaui); whereas Rocha and Bowen contend that parapatric speciation is the primary mode among coral-reef fish. Evidence for a clinal model of parapatric speciation was found to occur in Salpidae.
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Futuyama and Mayer contend that this form of parapatric speciation is untenable and that chromosomal rearrangements are unlikely to cause speciation. Nevertheless, data does support that chromosomal rearrangements can possibly lead to reproductive isolation, but it does not mean speciation results as a consequence.
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Very few laboratory studies have been conducted that explicitly test for parapatric speciation. However, research concerning sympatric speciation often lends support to the occurrence of parapatry. This is due to the fact that, in symaptric speciation, gene flow within a population is unrestricted; whereas in parapatric speciation, gene flow is limited—thus allowing reproductive isolation to evolve easier. Ödeen and Florin complied 63 laboratory experiments conducted between the years 1950–2000 (many of which were discussed by Rice and Hostert previously) concerning sympatric and parapatric speciation.
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The phylogenetic signature of this model is that the central population becomes derived, while the peripheral isolates stay pleisomorphic—the reverse of the general model. In contrast to centrifugal speciation, peripatric speciation has sometimes been referred to as centripetal speciation (see figures 1 and 2 for a contrast). Centrifugal speciation has been largely ignored in the scientific literature, often dominated by the traditional model of peripatric speciation. Despite this, Brown cited a wealth of evidence to support his model, of which has not yet been refuted.
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The key difference between ecological speciation and other kinds of speciation, is that it is triggered by divergent natural selection among different habitats; as opposed to other kinds of speciation processes, like random genetic drift, the fixation of incompatible mutations in populations experiencing similar selective pressures, or various forms of sexual selection not involving selection on ecologically relevant traits. Ecological speciation can occur either in allopatry, sympatry, or parapatry. The only requirement being that speciation occurs as a result of adaptation to different ecological or micro-ecological conditions. Some debate exists over the framework concerning the delineation of whether a speciation event is ecological or nonecological.
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Early speciation research typically reflected geographic distributions and were thus termed geographic, semi-geographic, and non- geographic. Geographic speciation corresponds to today's usage of the term allopatric speciation, and in 1868, Moritz Wagner was the first to propose the concept of which he used the term Separationstheorie. His idea was later interpreted by Ernst Mayr as a form of founder effect speciation as it focused primarily on small geographically isolated populations. Edward Bagnall Poulton, an evolutionary biologist and a strong proponent of the importance of natural selection, highlighted the role of geographic isolation in promoting speciation, in the process coining the term "sympatric speciation" in 1903.Mayr, Ernst 1942.
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In L. V. Giddings, K. Y. Kaneshiro, and W. W. Anderson. (eds) Genetics, Speciation, and the Founder Principle, Oxford University Press, New York, Pp. 43–76. Selection's role in speciation is widely supported, whereas founder effect speciation is not, having been subject to a number of criticisms.
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"Speciation in the fossil record." In Erwin, D.H. & Anstey, R.L. (eds). New Approaches to Speciation in the Fossil Record. Columbia University Press, New York, pp. 11–39.
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Ecological selection is "the interaction of individuals with their environment during resource acquisition". Natural selection is inherently involved in the process of speciation, whereby, "under ecological speciation, populations in different environments, or populations exploiting different resources, experience contrasting natural selection pressures on the traits that directly or indirectly bring about the evolution of reproductive isolation". Evidence for the role ecology plays in the process of speciation exists. Studies of stickleback populations support ecologically linked speciation arising as a by-product, alongside numerous studies of parallel speciation—of which, substantiates speciation's occurrence in nature.
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Typically independent speciation does not significantly alter the phylogenetic analysis used to measure cospeciation. However, in combination with extinction, independent speciation can become very problematic when trying to sort out host and parasite phylogenies. Independent speciation occurs when a single population on a single host undergoes speciation resulting in two sister lineages of parasite on a particular host. In other words, the parasite lineage speciates while the host lineage does not.
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He studied the mechanisms of sympatric speciation of cichlids in crater lakes,Schliewen, U.K., Tautz, D., Pääbo, S. (1994). Sympatric speciation suggested by monophyly of crater lake cichlids. Nature, 368, 629-632. hybrid speciation of sculpins in the Rhine systemNolte, A.W., Freyhof, J., Stemshorn, K.C., Tautz, D. (2005).
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Researchers consider reproductive isolation as key to speciation. A major aspect of speciation research is to determine the nature of the barriers that inhibit reproduction. Botanists often consider the zoological classifications of prezygotic and postzygotic barriers as inadequate. The examples provided below give insight into the process of speciation.
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Heteropatric speciation is a special case of sympatric speciation that occurs when different ecotypes or races of the same species geographically coexist but exploit different niches in the same patchy or heterogeneous environment. It is thus is a refinement of sympatric speciation, with a behavioral, rather than geographical barrier to the flow of genes among diverging groups within a population. Behavioral separation as a mechanism for promoting sympatric speciation in a heterogeneous (or patchwork landscape) was highlighted in John Maynard Smith's seminal paper on sympatric speciation. In recognition of the importance of this behavioral versus geographic distinction, Wayne Getz and Veijo Kaitala introduced the term heteropatry in their extension of Maynard Smiths' analysis of conditions that facilitate sympatric speciation.
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After that, sympatric speciation fell out of favor with biologists and has only recently seen a resurgence in interest. Some biologists, such as James Mallet, believe that Darwin's view on speciation was misunderstood and misconstrued by Mayr. Today, sympatric speciation is supported by evidence from laboratory experiments and observations from nature.
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It is well established that, "...natural selection is a ubiquitous part of speciation...", and is the primary driver of speciation; therefore, the following examples of natural selection and speciation will often interdepend or correspond with one another. The examples below are only a small fraction of the actual experiments and observations.
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In sympatry m=0.5, while in parapatric speciation, 0 < m < 0.5 represents the entire continuum, though not all scientists accept this geographic mode classification scheme, which does not necessarily reflect the complexity of speciation. Allopatry is often regarded as the default or "null" model of speciation, but this too is debated.
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Animal species and evolution. Harvard University Press, Cambridge. The mechanisms are genetically controlled and can appear in species whose geographic distributions overlap (sympatric speciation) or are separate (allopatric speciation).
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Peripatric speciation was originally proposed by Ernst Mayr in 1954, and fully theoretically modeled in 1982.Ernst Mayr. (1982). Processes of speciation in animals. In A. R. I. Liss.
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In 1976 and 1980, the Kaneshiro model of peripatric speciation was developed by Kenneth Y. Kaneshiro which focused on sexual selection as a driver for speciation during population bottlenecks.
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The evolutionary process by which biological populations evolve to become distinct or reproductively isolated as species is called speciation. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species. Speciation depends on a measure of reproductive isolation, a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate.
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Spartina and Senecio), but allopolyploids can also form via fertile intermediate hybrids (e.g. Tragopogon). In general, hybrid species can arise from two major types of hybrid speciation, defined by whether the speciation event is associated with genome duplication (polyploidy) or not. Homoploid hybrid speciation Homoploid hybrid speciation is defined as the evolution of a new hybrid species with reproductive isolation to both parent taxa without change of ploidy, i.e. number of chromosome sets.
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Parapatric speciation It was originally assumed that geographic isolation was a necessary precursor to speciation (allopatric speciation). The possibility that clines may be a precursor to speciation was therefore ignored, as they were assumed to be evidence of the fact that in contiguous populations gene flow was too strong a force of homogenisation, and selection too weak a force of differentiation, for speciation to take place. However, the existence of particular types of clines, such as ring species, in which populations did not differentiate in allopatry but the terminal ends of the cline nonetheless do not interbreed, cast into doubt whether complete geographical isolation of populations is an absolute requirement for speciation. Because clines can exist in populations connected by some degree of gene flow, the generation of new species from a previously clinal population is termed parapatric speciation.
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Sympatry has been increasingly evidenced in current research. Because of this, sympatric speciation – which was once highly debated among researchers – is progressively gaining credibility as a viable form of speciation.
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Other potential mechanisms for nonecological speciation include mutation-order speciation and changes in chirality in gastropods. Nonecological speciation might not be accompanied by strong morphological differentiation, so might give rise to cryptic species, however there are some species that are difficult for humans to differentiate that are strongly differentiated with respect to their resource use, and so are likely a result of ecological speciation (e.g., host shifts in parasites or phytophagous insects). When species recognition/sexual selection plays a strong role in maintaining species boundaries, the species generated by nonecological speciation might be straightforward for humans to differentiate, as in some odonates.
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Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them. Nevertheless, the primary characteristic of peripatric speciation proposes that one of the populations is much smaller than the other. The terms peripatric and peripatry are often used in biogeography, referring to organisms whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur—for example on an oceanic island compared to the mainland.
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Reinforcement has been a contentious factor in speciation. It is more often invoked in sympatric speciation studies, as it requires gene flow between two populations. However, reinforcement may also play a role in allopatric speciation, whereby the reproductive barrier is removed, reuniting the two previously isolated populations. Upon secondary contact, individuals reproduce, creating low-fitness hybrids.
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This ability is achievable by host switching, which promotes speciation.
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Evidence for the occurrence of this type of speciation has been found in several plant species pairs: Layia discoidea and L. glandulosa, Clarkia lingulata and C. biloba, and Stephanomeria malheurensis and S. exigua ssp. coronaria. A closely related model of peripatric speciation is called budding speciation—largely applied in the context of plant speciation. The budding process, where a new species originates at the margins of an ancestral range, is thought to be common in plants—especially in progenitor-derivative species pairs.
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Research has well established the fact that interspecific mate discrimination occurs to a greater extent between sympatric populations than it does in purely allopatric populations; however, other factors have been proposed to account for the observed patterns. Reinforcement in allopatry has been shown to occur in nature (evidence for speciation by reinforcement), albeit with less frequency than a classic allopatric speciation event. A major difficulty arises when interpreting reinforcement's role in allopatric speciation, as current phylogenetic patterns may suggest past gene flow. This masks possible initial divergence in allopatry and can indicate a "mixed-mode" speciation event—exhibiting both allopatric and sympatric speciation processes.
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Leslie D. Gottlieb pointing to Stephanomeria malheurensis Photo taken by Ken Chambers Gottlieb was occupied with new species formation via "quantum speciation" throughout his career. As defined by Verne Grant, and cited by Gottlieb in his 2003 summary of the subject in plants "we can define quantum speciation as the budding off of a new and very different daughter species from a semi-isolated peripheral population of the ancestral species in a cross-fertilizing organism...as compared with geographical speciation, which is a gradual and conservative process, quantum speciation is rapid and radical in its phenotypic or genotypic effects or both." Grant thought that it would be accompanied by inbreeding in the founder population. Therefore, "quantum speciation" would be related to, if not identical with, in Gottlieb's use of the term, sympatric speciation.
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When speciation is not driven by (or strongly correlated with) divergent natural selection, it can be said to be nonecological, so as to distinguish it from the typical definition of ecological speciation: "It is useful to consider ecological speciation as its own form of species formation because it focuses on an explicit mechanism of speciation: namely divergent natural selection. There are numerous ways other than via divergent natural selection in which populations might become genetically differentiated and reproductively isolated." It is likely that many instances of nonecological speciation are allopatric, especially when the organisms in question are poor dispersers (e.g., land snails, salamanders), however sympatric nonecological speciation may also be possible, especially when accompanied by an "instant" (at least in evolutionary time) loss of reproductive compatibility, as when polyploidization happens.
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Additionally, these subspecies are rarely recorded to have hybrid offspring, which further suggests that there is complete speciation due to mating call differences. The differences in mating calls also help to reinforce the speciation process.
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They also state that under this definition, sympatric speciation seems plausible.
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These are effectively models of reinforcement or "mixed-mode" speciation events.
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Evidence for speciation by reinforcement has been accumulating since the 1990s.
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Anthoxanthum odoratum is experiencing speciation parapatrically in areas of mine contamination.
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In the plain tiger butterfly, the consequences have led to speciation.
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Since then, other alternative models have been developed such as centrifugal speciation, that posits that a species' population experiences periods of geographic range expansion followed by shrinking periods, leaving behind small isolated populations on the periphery of the main population. Other models have involved the effects of sexual selection on limited population sizes. Other related models of peripherally isolated populations based on chromosomal rearrangements have been developed such as budding speciation and quantum speciation. The existence of peripatric speciation is supported by observational evidence and laboratory experiments.
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"The pervasive effect of selection suggests that adaptive evolution and speciation are inseparable, casting doubt on whether speciation is ever nonecological". However, there are numerous examples of closely related, ecologically similar species (e.g., Albinaria land snails on islands in the Mediterranean, Batrachoseps salamanders from California, and certain crickets and damselflies), which is a pattern consistent with the possibility of nonecological speciation.
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A survey of the rates of speciation in fish and their associated hybrid zones found similar patterns in sympatry, supporting the occurrence of reinforcement.A. R. McCune and N. R. Lovejoy. (1998). The relative rate of sympatric and allopatric speciation in fishes. In D. J. Howard and S. H. Berlocher (eds) Endless Forms: Species and Speciation, Oxford University Press, pp. 172–185.
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New York: Columbia Univ. Press, p. 390. Eldredge and Gould relied upon ordinary speciation, particularly Ernst Mayr's concept of allopatric speciation. Lastly, and perhaps most significantly, quantum evolution took no position on the issue of stasis.
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Such organisms are usually closely related (e.g. sister species); their distribution being the result of peripatric speciation. The concept of peripatric speciation was first outlined by the evolutionary biologist Ernst Mayr in 1954.Ernst Mayr. (1954).
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Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication On the Origin of Species. In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences between the productions of various regions [of the world]". F. J. Sulloway contends that Darwin's position on speciation was "misleading" at the least and may have later misinformed Wagner and David Starr Jordan into believing that Darwin viewed sympatric speciation as the most important mode of speciation. Nevertheless, Darwin never fully accepted Wagner's concept of geographical speciation.
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Speciation has largely been divided into discrete modes that correspond to rates of gene flow between two incipient populations. Today however, research has driven the development of alternative schemes and the discovery of new processes of speciation.
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Darwin instead saw speciation as occurring by species entering new ecological niches.
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After the synthesis, speciation research continued largely within natural history and biogeography — with much less emphasis on genetics. The study of speciation has seen its largest increase since the 1980s with an influx of publications and a host of new terms, methods, concepts, and theories. This "third phase" of work — as Jerry A. Coyne and H. Allen Orr put it — has led to a growing complexity of the language used to describe the many processes of speciation. The research and literature on speciation have become, "enormous, scattered, and increasingly technical".
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Researchers have long debated the roles of sexual selection, natural selection, and genetic drift in speciation. Darwin extensively discussed sexual selection, with his work greatly expanded on by Ronald Fisher; however, it was not until 1983 that the biologist Mary Jane West-Eberhard recognized the importance of sexual selection in speciation. Natural selection plays a role in that any selection towards reproductive isolation can result in speciation — whether indirectly or directly. Genetic drift has been widely researched from the 1950s onwards, especially with peak-shift models of speciation by genetic drift.
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It is believed that disruptive selection is one of the main forces that drive sympatric speciation in natural populations. The pathways that lead from disruptive selection to sympatric speciation seldom are prone to deviation; such speciation is a domino effect that depends on the consistency of each distinct variable. These pathways are the result of disruptive selection in intraspecific competition; it may cause reproductive isolation, and finally culminate in sympatric speciation. It is important to keep in mind that disruptive selection does not always have to be based on intraspecific competition.
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Ecological speciation can occur allopatrically, sympatrically, or parapatrically; the only requirement being that it occurs as a result of adaptation to different ecological or micro-ecological conditions. Ecological allopatry is a reverse- ordered form of allopatric speciation in conjunction with reinforcement. First, divergent selection separates a non-allopatric population emerging from pre-zygotic barriers, from which genetic differences evolve due to the obstruction of complete gene flow. The terms allo-parapatric and allo- sympatric have been used to describe speciation scenarios where divergence occurs in allopatry but speciation occurs only upon secondary contact.
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A. R. McCune and N. R. Lovejoy. (1998). The relative rate of sympatric and allopatric speciation in fishes. In D. J. Howard and S. H. Berlocher (eds) Endless Forms: Species and Speciation, Oxford University Press, pp. 172–185.
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Different modes of speciation The lack of geographic constraint in isolating sympatric populations implies that the emerging species avoid interbreeding via other mechanisms. Before speciation is complete, two diverging populations may still produce viable offspring. As speciation progresses, isolating mechanisms – such as gametic incompatibility that renders fertilization of the egg impossible – are selected for in order to increase the reproductive divide between the two populations.
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The succession of fossils in stratigraphy can be used to determine evolutionary trends among fossil organisms. In addition, incidences of speciation can be interpreted from the data and numerous studies have been conducted documenting both morphological evolution and speciation.
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Oceanic islands and archipelagos provide the strongest empirical evidence that peripatric speciation occurs.
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Rapid allopatric speciation in logperch darters (Percidae: Percina). Evolution 58(12): 2798-2808.
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These recognition signals could then play a role in reproductive isolation and speciation.
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Haploidy or diploidy: which is better? Nature 351:314-315 his work on sympatric speciation,Kondrashov AS & Kondrashov FA. 1999. Interactions among quantitative traits in the course of symaptric speciation. Nature 400: 351-354 and his work on evaluating mutation rates.
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Mulga, Central Australia Insect-plant interactions have been important in defining models of coevolution and cospeciation, referring to whether plant speciation drives insect speciation and vice versa, though most herbivorous insects probably evolved long after the plants on which they feed.
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Encyclopedia of Insects. Academic Press. Examples of speciation come from the observations of island biogeography and the process of adaptive radiation, both explained previously. Evidence of common descent can also be found through paleontological studies of speciation within geologic strata.
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D. alloeum wasps attacking R. pomonella in apples appear to be undergoing a speciation event in concert with their hosts.Forbes, A.A., L.L. Stelinski, T.H.Q. Powell, J.J. Smith and J.L. Feder. 2009. Sequential sympatric speciation across trophic levels. Science 323: 776-779.
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In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences between the productions of various regions [of the world]". F. J. Sulloway contends that Darwin's position on speciation was "misleading" at the least and may have later misinformed Wagner and David Starr Jordan into believing that Darwin viewed sympatric speciation as the most important mode of speciation. Nevertheless, Darwin never fully accepted Wagner's concept of geographical speciation. Ernst Mayr in 1994 David Starr Jordan played a significant role in promoting allopatric speciation in the early 20th century, providing a wealth of evidence from nature to support the theory.
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Positive assortative mating is a key element leading to reproductive isolation within a species, which in turn may result speciation in sympatry over time. Sympatric speciation is defined as the evolution of a new species without geographical isolation. Speciation from assortative mating has occurred in the Middle East blind mole rat, cicadas, and the European corn borer. Humans display these genetic results of assortative mating too, just like other animals.
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Hybridization without change in chromosome number is called homoploid hybrid speciation. It is considered very rare but has been shown in Heliconius butterflies and sunflowers. Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. Polyploidy is a mechanism that has caused many rapid speciation events in sympatry because offspring of, for example, tetraploid x diploid matings often result in triploid sterile progeny.
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As such, allopatry is a geographical distribution opposed to sympatry (speciation within the same area). Furthermore, the terms allopatric, vicariant, and geographical speciation are often used interchangeably in the scientific literature. This article will follow a similar theme, with the exception of special cases such as peripatric, centrifugal, among others. Observation of nature creates difficulties in witnessing allopatric speciation from "start-to-finish" as it operates as a dynamic process.
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Centrifugal speciation is a variant, alternative model of peripatric speciation. This model contrasts with peripatric speciation by virtue of the origin of the genetic novelty that leads to reproductive isolation. When a population of a species experiences a period of geographic range expansion and contraction, it may leave small, fragmented, peripherally isolated populations behind. These isolated populations will contain samples of the genetic variation from the larger parent population.
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Molecular evolution, adaptive radiation, and geographic speciation in Cyanea (Campanulaceae, Lobeliodeae). Pp. 259-301 in W.L. Wagner and V.A. Funk (eds.) Hawaiian Biogeography: Evolution on a Hot- Spot Archipeligo. Smithsonian Institution Press, Washington DC. Other endemic species in Hawaii also provide evidence of peripatric speciation such as the endemic flightless crickets (Laupala). It has been estimated that, "17 species out of 36 well-studied cases of [Laupala] speciation were peripatric".
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Recently, biologists have increasingly recognized that hybrid speciation can occur in animals as well.
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In South America, however, vicariance appears to have played an important role in speciation.
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Consequently, these species may be the result of allopatric speciation in ice age refugia.
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Prior to speciation of the hosts, if the distribution of the parasite population among the host population is sporadic, it is possible that when host speciation occurs, it will occur with hosts that do not have the parasite population. This phenomenon is known as "missing the boat". The parasites could potentially cospeciate with their host down the line, however, the parasites could potentially be absent from some host lineages. Like extinction and independent speciation, "missing the boat" alone will probably have a minimal effect on mapping phylogenies, however, in conjunction with independent speciation, parasite and host phylogenies can begin to break apart.
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However, Mayr's view has not been entirely accepted, as Darwin's transmutation notebooks contained writings concerning the role of isolation in the splitting of species. Furthermore, Many of Darwin's ideas on speciation largely match the modern theories of both adaptive radiation and ecological speciation.
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Current evidence done with molecular clock analyses revealed that much of the speciation of the group occurred during periods of intense climate change associated with the last ice ages, with especially high speciation rates being observed in salmonids that developed an anadromous lifestyle.
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Parapatric speciation may also result from reproductive isolation caused by social selection: individuals interacting altruistically.
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This is known as reinforcement and plays an important role in parapatric and sympatric speciation.
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This focus on ecology generated a host of new terms relating to the barriers to reproduction (e.g. allochronic speciation, in which gene flow is reduced or removed by timing of breeding periods; or habitat isolation, in which species occupy different habitats within the same area). Sympatric speciation, regarded by Mayr as unlikely, has become widely accepted. Research on the influence of natural selection on speciation, including the process of reinforcement, has grown.
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Isolated and relatively homogeneous habitats such as crater lakes and islands are among the best geographical settings in which to demonstrate sympatric speciation. For example, Nicaragua crater lake cichlid fishes include nine described species and dozens of undescribed species that have evolved by sympatric speciation. Monostroma latissimum, a marine green algae, also shows sympatric speciation in southwest Japanese islands. Although panmictic, the molecular phylogenetics using nuclear introns revealed staggering diversification of population.
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The emerged adult beetles mate assortatively, meaning they mate with others that developed on the same host bean. If the hybrids of the population are less fit, assortative mating can lead to speciation. One study looked at this and found speciation beginning to occur in early generations but because there was no selection against hybrids, recombination destroyed any linkage that was formed between host and mating preference which did not allow speciation to be completed.
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Furthermore, the number of endemics on an island is directly correlated with the relative isolation of the island and its area. In some cases, speciation on islands has occurred rapidly. Dispersal and in situ speciation are the agents that explain the origins of the organisms in Hawaii. Various geographic modes of speciation have been studied extensively in Hawaiian biota, and in particular, angiosperms appear to have speciated predominately in allopatric and parapatric modes.
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A species of catfish from the genus Parauchenoglanis has been introduced to the lake, and this probably presents a serious threat to the endemic cichlids. The Ejagham cichlids are commonly considered a prime example of sympatric speciation within its two genera. Studies indicate a level of secondary gene flow between the lake's species and relatives from nearby regions, and this likely facilitated the speciation (i.e., the Ejagham species not strictly the result of sympatric speciation).
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William Louis Brown, Jr. proposed an alternative model of peripatric speciation in 1957 called centrifugal speciation. This model contrasts with peripatric speciation by virtue of the origin of the genetic novelty that leads to reproductive isolation. A population of a species experiences periods of geographic range expansion followed by periods of contraction. During the contraction phase, fragments of the population become isolated as small refugial populations on the periphery of the central population.
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In allopatric speciation, a species population becomes separated by a geographic barrier, whereby reproductive isolation evolves producing two separate species. From this, if a recently separated population comes in contact again, low fitness hybrids may form, but reinforcement acts to complete the speciation process.
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De Vos, J. 1996. Taxonomy, Ancestry and Speciation of the Endemic Pleistocene Deer of Crete Compared with the Taxonomy, Ancestry and Speciation of Darwin's Finches. In: Reese, 1996, 111-24. identified eight morphotypes into one genus (Candiacervus), whereas Capasso Barbato (1992)Capasso Barbato L. 1992b.
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George Romanes later adopted this terminology during his evolutionary studies. Gulick later proposed general geographic models of speciation, and disputed Moritz Wagner's more extreme claims that geographic speciation was the only possible route to speciation.Gulick J.T. 1908. Isolation and selection in the evolution of species.
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Some of his work was posthumously published by his wife Elizaveta Lukina (who was also a research collaborator). Promptov examined speciation processes and noted that song variation was through both heredity and learning. Promptov's speciation concept was ignored by proponents of the modern evolutionary synthesis.
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Speciation theory caused by mountain ranges and Pleistocene glacial cycles: It is believed that many of the Iberolacerta genus had led to many speciation seen today because of the Pleistocene glacial cycles and Holocene habitat fragmentation.Crochet PA, Chaline O, Surget-Groba Y, Debain C, Cheylan M (2004) "Speciation in mountains: phylogeography and phylogeny of the rock lizards genus Iberolacerta (Reptilia: Lacertidae)". Mol Phylogenet Evol 30: 860–866 For example, I. monticola has been studied to determine its cause of speciation. There was an analysis of 17 I. monticola population's mitochondrial DNA sequences, at a control region and cytochrome b loci, throughout the northwestern quadrant of the Iberian Peninsula.
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Sympatric pitcher plants, Nepenthes jamban (left) and Nepenthes lingulata (right) in Sumatran upper montane forest In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation. Such speciation may be a product of reproductive isolation – which prevents hybrid offspring from being viable or able to reproduce, thereby reducing gene flow – that results in genetic divergence. Sympatric speciation does not imply secondary contact, which is speciation or divergence in allopatry followed by range expansions leading to an area of sympatry.
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Allopatric speciation (from Ancient Greek ἄλλος, allos, meaning "other", and πατρίς, patris, "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow. Various geographic changes can arise such as the movement of continents, and the formation of mountains, islands, bodies of water, or glaciers. Human activity such as agriculture or developments can also change the distribution of species populations. These factors can substantially alter a region's geography, resulting in the separation of a species population into isolated subpopulations.
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Due to the continuous nature of a parapatric population distribution, population niches will often overlap, producing a continuum in the species’ ecological role across an environmental gradient. Whereas in allopatric or peripatric speciation—in which geographically isolated populations may evolve reproductive isolation without gene flow—the reduced gene flow of parapatric speciation will often produce a cline in which a variation in evolutionary pressures causes a change to occur in allele frequencies within the gene pool between populations. This environmental gradient ultimately results in genetically distinct sister species. Fisher's original conception of clinal speciation relied on (unlike most modern speciation research) the morphological species concept.
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In a ring species, individuals are able to successfully reproduce (exchange genes) with members of their own species in adjacent populations occupying a suitable habitat around a geographic barrier. Individuals at the ends of the cline are unable to reproduce when they come into contact. The concept of a ring species is associated with allopatric speciation as a special case; however, Coyne and Orr argue that Mayr's original conception of a ring species does not describe allopatric speciation, "but speciation occurring through the attenuation of gene flow with distance". They contend that ring species provide evidence of parapatric speciation in a non-conventional sense.
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Parallel speciation is where "greater reproductive isolation repeatedly evolves between independent populations adapting to contrasting environments than between independent populations adapting to similar environments". It is established that ecological speciation occurs and with much of the evidence, "...accumulated from top-down studies of adaptation and reproductive isolation".
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Sympatric speciation suggested by monophyly of crater lake cichlids. Nature 368(6472): 629–632. These cichlids are commonly recognized as a prime example of sympatric speciation, but studies indicate that they were not the result of a single founding event.Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015).
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41.24% of all known species of fish are found in fresh water. This is primarily due to the rapid speciation that the scattered habitats make possible. When dealing with ponds and lakes, one might use the same basic models of speciation as when studying island biogeography.
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However, he did not recognize that the pattern was due to speciation. One naturalist, Leopold von Buch (1825) did recognize the geographic patterns and explicitly stated that geographic isolation may lead to species separating into new species. Mayr suggests that Von Buch was likely the first naturalist to truly suggest geographic speciation. Other naturalists, such as Henry Walter Bates (1863), recognized and accepted the patterns as evidence of speciation, but in Bate's case, did not propose a coherent model.
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Investigating the possibility of sympatric speciation requires a definition thereof, especially in the 21st century, when mathematical modeling is used to investigate or to predict evolutionary phenomena. Much of the controversy concerning sympatric speciation may lie solely on an argument over what sympatric divergence actually is. The use of different definitions by researchers is, sadly, a great impediment to empirical progress on the matter. The dichotomy between sympatric and allopatric speciation is no longer accepted by the scientific community.
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Reinforcement assists speciation by selecting against hybrids. Reinforcement is a process within speciation where natural selection increases the reproductive isolation between two populations of species by reducing the production of hybrids. Evidence for speciation by reinforcement has been gathered since the 1990s, and along with data from comparative studies and laboratory experiments, has overcome many of the objections to the theory. Differences in behavior or biology that inhibit formation of hybrid zygotes are termed prezygotic isolation.
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In peripatric speciation, a small, isolated population on the periphery of a central population evolves reproductive isolation due to the reduction or elimination of gene flow between the two. Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. If a small population of a species becomes isolated (e.g. a population of birds on an oceanic island), selection can act on the population independent of the parent population.
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Such a process can happen through allopatric speciation, whereby species diverge according to different selection pressures in different geographical areas, or through sympatric speciation, by which new species evolve from a common ancestor while remaining in the same area. In Lake Apoyo in Nicaragua, Amphilophus zaliosus and its sister species Amphilophus citrinellus display many of the criteria needed for sympatric speciation. In the African rift lake system, cichlid species in numerous distinct lakes evolved from a shared hybrid swarm.
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Some researchers even consider there to be a bias in reporting of positive allopatric speciation events, and in one study reviewing 73 speciation papers published in 2009, only 30 percent that suggested allopatric speciation as the primary explanation for the patterns observed considered other modes of speciation as possible. Contemporary research relies largely on multiple lines of evidence to determine the mode of a speciation event; that is, determining patterns of geographic distribution in conjunction with phylogenetic relatedness based on molecular techniques. This method was effectively introduced by John D. Lynch in 1986 and numerous researchers have employed it and similar methods, yielding enlightening results. Correlation of geographic distribution with phylogenetic data also spawned a sub-field of biogeography called vicariance biogeography developed by Joel Cracraft, James Brown, Mark V. Lomolino, among other biologists specializing in ecology and biogeography.
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The geographic separation and subsequent genetic isolation of portions of an ancestral population can result in speciation.
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Alternatively, N. murudensis may have evolved from populations of N. tentaculata that underwent speciation, possibly in isolation.
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Endemism in the australian flora. Journal of Biogeography 28: 183-198. supporting speciation and biodiversity.Low, T. 2011.
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In Clarkia, we have not observed marked changes in > physiology and pattern of development that could be described as > macroevolution. Reorganization of the genomes may, however, set the stage > for subsequent evolution along a very different course from that of the > ancestral populations Harlan Lewis refined this concept in a 1962 paper where he coined the term "Catastrophic Speciation" to describe this mode of speciation, since he theorized that the reductions in population size and consequent inbreeding that led to chromosomal rearrangements occurred in small populations that were subject to severe drought. Leslie D. Gottlieb in his 2003 summary of the subject in plants stated > we can define quantum speciation as the budding off of a new and very > different daughter species from a semi-isolated peripheral population of the > ancestral species in a cross-fertilizing organism...as compared with > geographical speciation, which is a gradual and conservative process, > quantum speciation is rapid and radical in its phenotypic or genotypic > effects or both. Gottlieb did not believe that sympatric speciation required disruptive selection to form a reproductive isolating barrier, as defined by Grant, and in fact Gottlieb stated that requiring disruptive selection was "unnecessarily restrictive" in identifying cases of sympatric speciation.
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In essence, sympatric speciation does require very strong forces of natural selection to be acting on heritable traits, as there is no geographic isolation to aid in the splitting process. Yet, recent research has begun to indicate that sympatric speciation is not as uncommon as was once assumed.
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A major outcome of multi- generational natal philopatry is genetic divergence and, ultimately, speciation. Without genetic exchange, geographically and reproductively isolated populations may undergo genetic drift. Such speciation is most evident on islands. For mobile island-breeding animals, finding a new breeding location may be beyond their means.
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The basis for advancing the multiregional interpretation stems from his skepticism of punctuated equilibrium (the idea evolution typically proceeds with long static periods and abrupt changes, instead of gradual modification during speciation) as an accurate model for Pleistocene humanity, noting that speciation played a role earlier in human evolution.
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Here, the geographic modes of speciation are classified as types of assortive mating. Fitzpatrick and colleagues believe that the biogeographic scheme "is a distraction that could be positively misleading if the real goal is to understand the influence of natural selection on divergence." They maintain that, to fully understand speciation, "the spatial, ecological, and genetic factors" involved in divergence must be explored. Sara Via recognizes the importance of geography in speciation but suggests that classification under this scheme be abandoned.
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The theory of Pleistocene refugia was developed by Jürgen Haffer in 1969 with his article Speciation of Amazonian Forest Birds. Haffer proposed the explanation for speciation was the product of rainforest patches being separated by stretches of non-forest vegetation during the last glacial period. He called these patches of rainforest areas refuges and within these patches allopatric speciation occurred. With the end of the glacial period and increase in atmospheric humidity, rainforest began to expand and the refuges reconnected.
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Sympatric speciation, where reproductive isolation evolves within a population without the aid of geographic barriers. Speciation describes when two populations diverge sufficiently such that they are considered different species, often because they can no longer successfully reproduce with one another. This process is intuitive for conspicuous examples such as ring species, wherein a population splits due to a geographical barrier such as a mountain range, leading to allopatric populations. However why species diverge when their geographic ranges overlap (sympatric speciation) is less understood.
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In: Mechanisms of Speciation (A. R. I. Liss, ed.), pp. 1–19. Alan R. Liss Inc., New York.
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The concept of incomplete lineage sorting ultimately reflects on persistence of polymorphisms across one or more speciation events.
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Mimicry, hybridization, and co-evolution with host plants have probably contributed to speciation in the butterflies (Lamas, 2008).
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Cheng, Heng. "From Lakes to Oceans: Speciation of Sockeye Salmon and Other Fishes." Emory Scholars Blog. Emory University.
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The ability of the speciation techniques (multi-method approach) to provide a chemically significant description of the kinetics of metal-natural ligands interaction in sediment suggests that the metal and ligand exchange reactions precede mainly by the disjunctive mechanism (complete dissociation of ML), a fundamental process in coastal marine systems. He showed that kinetics-based approach provides the actual metal speciation instead of the current practice of chemical equilibrium speciation. This kinetic based is expected to promote wider acceptance of the approach by regulatory agencies. He has demonstrated the effects of Ligand Field Stabilization Energy, water exchange rate, Jahn Teller distortion of transition metals on their speciation and bioavailability in estuarine and coastal sediments.
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Speciation is the evolutionary process by which new biological species arise. Biologists research species using different theoretical frameworks for what constitutes a species (see species problem and species complex) and there exists debate with regard to delineation. Nevertheless, much of the current research suggests that, "...speciation is a process of emerging genealogical distinctness, rather than a discontinuity affecting all genes simultaneously" and, in allopatry (the most common form of speciation), "reproductive isolation is a byproduct of evolutionary change in isolated populations, and thus can be considered an evolutionary accident". Speciation occurs as the result of the latter (allopatry); however, a variety of differing agents have been documented and are often defined and classified in various forms (e.g.
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This stricter definition includes polyploid hybrid taxa but only encompasses a handful of well studied cases of homoploid hybrid speciation, e.g. Heliconius heurippa, Passer italiae, and three Helianthus sunflower species because for most suggested examples of homoploid hybrid speciation, the genetic basis of reproductive isolation is still unknown. Hybrid species can occupy an ecological niche different to those of the parents and may be isolated from the parent species primarily through pre- mating barriers (hybrid speciation with external barriers). Hybrid species may also be reproductively isolated from the parent species through sorting of incompatibilities leading to new combinations of parental alleles that are incompatible with both parent species but compatible within the hybrid taxon (recombinational hybrid speciation).
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Observational evidence and laboratory experiments support the occurrence of peripatric speciation. Islands and archipelagos are often the subject of speciation studies in that they represent isolated populations of organisms. Island species provide direct evidence of speciation occurring peripatrically in such that, "the presence of endemic species on oceanic islands whose closest relatives inhabit a nearby continent" must have originated by a colonization event. Comparative phylogeography of oceanic archipelagos shows consistent patterns of sequential colonization and speciation along island chains, most notably on the Azores islands, Canary Islands, Society Islands, Marquesas Islands, Galápagos Islands, Austral Islands, and the Hawaiian Islands—all of which express geological patterns of spatial isolation and, in some cases, linear arrangement.
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The significance of responses of the genome to challenge. Science Vol. 226, pp. 792-801. Saltational speciation, also known as abrupt speciation, is the discontinuity in a lineage that occurs through genetic mutations, chromosomal aberrations or other evolutionary mechanisms that cause reproductively isolated individuals to establish a new species population.
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In this case, divergence is facilitated by the absence of gene flow. Parapatric speciation is the evolution of geographically adjacent populations into distinct species. In this case, divergence occurs despite limited interbreeding where the two diverging groups come into contact. In sympatric speciation, there is no geographic constraint to interbreeding.
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When Eldredge and Gould published their 1972 paper, allopatric speciation was considered the "standard" model of speciation. This model was popularized by Ernst Mayr in his 1954 paper "Change of genetic environment and evolution," and his classic volume Animal Species and Evolution (1963).Mayr, Ernst (1963). Animal Species and Evolution.
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The basic assumption underlying the mathematical model of cladistics is a situation where species split neatly in bifurcating fashion. While such an assumption may hold on a larger scale (bar horizontal gene transfer, see above), speciation is often much less orderly. Research since the cladistic method was introduced has shown that hybrid speciation, once thought rare, is in fact quite common, particularly in plants. Also paraphyletic speciation is common, making the assumption of a bifurcating pattern unsuitable, leading to phylogenetic networks rather than trees.
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Both hybridization and polyploidy have also been found to be major contributors to plant speciation. With the advent of molecular markers, "hybridization [is] considerably more frequent than previously believed". In addition to these two modes leading to speciation, pollinator preference and isolation, chromosomal rearrangements, and divergent natural selection have become critical to the speciation of plants. Furthermore, recent research suggests that sexual selection, epigenetic drivers, and the creation of incompatible allele combinations caused by balancing selection also contribute to the formation of new species.
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This type of speciation is most often sympatric speciation: where two or more species are created from an existing parent species that all live in the same geographic location. Although there is an absence of research on mammals and birds, this phenomenon has been heavily researched in several frog species around the world. The examples below illuminate speciation due to mating call differences in several frog species around the world. These distinct species are included because they are the focus of the majority of current research.
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In a DNA sequencing comparison involving species H. m. aglope, H. timareta, and H. m. amaryllis, it was found that gene sequences around mimicry loci were more recently diverged in comparison with the rest of the genome, providing evidence for speciation by hybridization over speciation by ancestral polymorphism.Joel Smith and Marcus R. Kronforst.
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Following the appearance of Anchiornis and other basal paravians, a series of vicariance events were inferred to have taken place. The widespread distribution and speciation of Dromaeosauridae and Troodontidae in Late Mesozoic coincided with the timing of the Pangean breakup, thus giving rise to the hypothesis of allopatric speciation initiated by continental fragmentation.
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Mashayekhi and Gras investigated the effect of spatial distribution and spatiotemporal information on speciation. In more recent research, Golestani et al. investigated how small, randomly distributed physical obstacles influence the distribution of populations and species, the level of population connectivity (e.g., gene flow), as well as the mode and tempo of speciation.
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Research documenting speciation is abundant. Biologists have documented numerous examples of speciation in nature—with evolution having produced far more species than any observer would consider necessary. For example, there are well over 350,000 described species of beetles.Liebherr, James K.; McHugh, Joseph V. in Resh, V. H.; Cardé, R. T. (Editors) 2003.
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Adaptive radiation, like the Galapagos finches observed by Charles Darwin, is often a consequence of rapid allopatric speciation among populations. However, in the case of the finches of the Galapagos, among other island radiations such as the honeycreepers of Hawaii represent cases of limited geographic separation and were likely driven by ecological speciation.
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Western Equatorial Crater Lakes. Early genetic evidence suggested that these probably were the result of sympatric speciation. Later studies indicate a level of secondary gene flow between the Bermin cichlids and Cross River C. guineensis, although it is unclear if this facilitated speciation among the former group. They are a relatively recent radiation.
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The major contributions made by Chakraborty in the field of Environmental Geochemistry (particularly in the field of trace and toxic metal speciation in marine systems) are described below: Since the marine systems are dynamic in nature and never at chemical equilibrium, He realized that chemical-equilibrium-based approach to do metal speciation would give wrong estimates of labile metal concentrations (which are widely correlated with ecotoxicity) in marine sediments. He improved kinetics-based approaches to understand metals speciation and their bioavailability in estuarine/coastal and deep sea systems. His research focuses on developing and applying a wide range of kinetic methods for chemical speciation in marine/estuarine sediment systems, each with its own characteristic timescale of measurement. An important achievement of his research is to advance the science of metal speciation by identifying the analytical timescale of measurement as the critical parameter for defining the chemical species in coastal and marine sediment system.
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Her investigations utilize genome research to further understand the complex and unique degree of speciation that occurs in lemur populations.
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Thus, the incipient separation of these faunas could have led to interchange in some but allopatric speciation in other groups.
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The SLMD can also be utilized for in-laboratory preconcentration and speciation of bioavailable trace metals from grab water samples.
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In fact Gottlieb's first publication on "sympatric speciation" in Stephanomeria', published in 1971, was summarised by him in the above 2003 paper on "quantum speciation." Gottlieb did not believe that sympatric speciation required disruptive selection to form a reproductive isolating barrier, as defined by Grant, and in fact Gottlieb stated that requiring disruptive selection was "unnecessarily restrictive" in identifying cases of sympatric speciation. In terminology used by Gottlieb, "progenitor species " would be the parental or "ancestral" species and the newly formed daughter species was "derived." In his first study of progenitor-derivative pairs of species, Gottlieb examined the diploid, geographically limited, self-pollinating derived species Stephanomeria malheurensis with the diploid, geographically widespread obligate outcrossing ancestral species Stephanomeria exicua ssp. coronaria.
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From the 1980s, new research tools increased the robustness of research, assisted by new methods, theoretical frameworks, models, and approaches. Coyne and Orr discuss the modern, post-1980s developments centered around five major themes: # genetics (also a primary factor in the Modern Synthesis), # molecular biology and analysis (namely, phylogenetics and systematics); # comparative analysis; # mathematical modeling and computer simulations; and # the role of ecology. Ecologists became aware that the ecological factors behind speciation were under-represented. This saw the growth in research concerning ecology's role in facilitating speciation — rightly designated ecological speciation.
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For most of the history of speciation, hybridization (polyploidy) has been a contentious issue, as botanists and zoologists have traditionally viewed hybridization's role in speciation differently. Carl Linnaeus was the earliest to suggest hybridization in 1760, Øjvind Winge was the first to confirm allopolyploidy in 1917, and a later experiment conducted by Clausen and Goodspeed in 1925 confirmed the findings. Today it is widely recognized as a common mechanism of speciation. Historically, zoologists considered hybridization to be a rare phenomenon, while botanists found it to be commonplace in plant species.
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Two species mate resulting in a fit hybrid that is unable to mate with members of its parent species. Hybrid speciation is a form of speciation where hybridization between two different species leads to a new species, reproductively isolated from the parent species. Previously, reproductive isolation between hybrids and their parents was thought to be particularly difficult to achieve, and thus hybrid species were thought to be extremely rare. With DNA analysis becoming more accessible in the 1990s, hybrid speciation has been shown to be a fairly common phenomenon, particularly in plants.
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Traits of the hybrids drive individuals to discriminate in mate choice, by which pre-zygotic isolation increases between the populations. Some arguments have been put forth that suggest the hybrids themselves can possibly become their own species: known as hybrid speciation. Reinforcement can play a role in all geographic modes (and other non-geographic modes) of speciation as long as gene flow is present and viable hybrids can be formed. The production of inviable hybrids is a form of reproductive character displacement, under which most definitions is the completion of a speciation event.
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Mountain building (orogeny) is directly correlated with—and directly affects biodiversity. The formation of the Himalayan mountains and the Qinghai–Tibetan Plateau for example have driven the speciation and diversification of numerous plants and animals such as Lepisorus ferns; glyptosternoid fishes (Sisoridae); and the Rana chensinensis species complex. Uplift has also driven vicariant speciation in Macowania daisies in South Africa's Drakensberg mountains, along with Dendrocincla woodcreepers in the South American Andes. The Laramide orogeny during the Late Cretaceous even caused vicariant speciation and radiations of dinosaurs in North America.
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As a traditionally-trained biologist, Mayr was often highly critical of early mathematical approaches to evolution, such as those of J.B.S. Haldane, and famously called such approaches "beanbag genetics" in 1959. He maintained that factors such as reproductive isolation had to be taken into account. In a similar fashion, Mayr was also quite critical of molecular evolutionary, studies such as those of Carl Woese. Current molecular studies in evolution and speciation indicate that although allopatric speciation is the norm, there are numerous cases of sympatric speciation in groups with greater mobility, such as birds.
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They are restricted to suitable breeding and feeding grounds, making novel niche exploration rare, particularly in fast flowing drainages. Low mobility is hypothesized to have facilitated speciation in regions where multiple species appear to have historical sympatric distributions. Various life history traits like body size determine the niche range available to a particular species (Knouft, 2004)The biogeographic dispersal model has been proposed as the most likely explanation of diversification and speciation of the subgenera. It has also been postulated that speciation occurred following niche partitioning, in response to competition where distributions overlap.
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For many years it has been suggested that sexual isolation caused by differences in mating behaviours is a precursor for reproductive isolation (lack of gene flow), and consequently speciation, in nature.Mayr, E. (1942). Systematics and Origin of Species, Belknap Press Mate choice behaviours are thought to be important forces that can result in speciation events because the strength of selection for attractive traits is often very strong. Speciation by this method occurs when a preference for some sexual trait shifts and produces a pre-zygotic barrier (preventing fertilisation).
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Depth-related adaptations, speciation processes and evolution of color in the genus Phyllidiopsis (Mollusca : Nudibranchia). Marine Biology 139(3):485-496.
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Charles Darwin was the first to suggest that sexual selection drives speciation; without it, complex life would probably not have evolved.
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Such phenomenon may lead to speciation and can occur if conditions in a local environment change dramatically through space or time.
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Examples of speciation affecting gene flow. When gene flow is blocked by physical barriers, this results in Allopatric speciation or a geographical isolation that does not allow populations of the same species to exchange genetic material. Physical barriers to gene flow are usually, but not always, natural. They may include impassable mountain ranges, oceans, or vast deserts.
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One of the potential evolutionary outcomes of hybridisation is the establishment of a novel, reproductively isolated lineage, i.e., hybrid speciation. A hybrid species has an admixed genome and forms stable genetically distinct populations. Some researchers argue that evidence of a hybridization-derived basis for reproductive isolation should be an additional defining criterion for hybrid speciation, but see.
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Cichlids such as Tropheops tropheops from Lake Malawi provide models for genome evolution. A major question of evolutionary biology is how genomes change to create new species. Speciation requires changes in behavior, morphology, physiology, or metabolism (or combinations thereof). The evolution of genomes during speciation has been studied only very recently with the availability of next-generation sequencing technologies.
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One variation of parapatric speciation involves species chromosomal differences. Michael J. D. White developed the stasipatric speciation model when studying Australian morabine grasshoppers (Vandiemenella). The chromosomal structure of sub- populations of a widespread species become underdominate; leading to fixation. Subsequently, the sub-populations expand within the species larger range, hybridizing (with sterility of the offspring) in narrow hybrid zones.
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These processes have been difficult to test until recently with advances in genetic modelling. Speciation by sexual selection is gaining popularity in the literature with increasing theoretical and empirical studies. There is evidence of early speciation through mate preference in guppies. Guppies are located across several isolated streams in Trinidad and male colour patterns differ geographically.
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As a result of duplication by speciation, a gene family might include 15 genes, one copy in each of 15 different species.
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Schliewen, U.K., Tautz, D., and Pääbo, S. (1994). Sympatric speciation suggested by monophyly of crater lake cichlids. Nature 368(6472): 629–632.
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White made important contributions to the development of cytology and cytogenetics. His work was influential in the study of speciation in biology.
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The biologist Ernst Mayr championed the concept of ring species, claiming that it unequivocally demonstrated the process of speciation. A ring species is an alternative model to allopatric speciation, "illustrating how new species can arise through 'circular overlap', without interruption of gene flow through intervening populations…" However, Jerry Coyne and H. Allen Orr point out that rings species more closely model parapatric speciation. Ring species often attract the interests of evolutionary biologists, systematists, and researchers of speciation leading to both thought provoking ideas and confusion concerning their definition. Contemporary scholars recognize that examples in nature have proved rare due to various factors such as limitations in taxonomic delineation or, "taxonomic zeal"—explained by the fact that taxonomists classify organisms into "species", while ring species often cannot fit this definition.
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The existence of this lake may have facilitated the diversification of Heleobia snails, but increased speciation only occurred during the subsequent Ballivian episode.
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This separates populations of some of the species in areas with different climates, forcing them to adapt, possibly giving rise to allopatric speciation.
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Some expand over time until the two populations fuse. Reinforcement may occur in hybrid zones. Hybrid zones are important study systems for speciation.
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Specialization on sunbirds vs other pollinators is thought to have contributed to plant speciation, including the exceptionally high flora diversity in southern Africa.
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Lenski notes that the rapid evolution of Cit+ was not necessarily unexpected since his team was also able to produce multiple Cit+ mutants in a few weeks during the replay experiments they reported in the 2008 paper in which his team first described the evolution of aerobic citrate use in the LTEE. Furthermore, Lenski criticizes Van Hofwegen et al.'s description of the initial evolution of Cit+ as a "speciation event" by pointing out that the LTEE was not designed to isolate citrate-using mutants or to deal with speciation since in their 2008 paper they said "that becoming Cit+ was only a first step on the road to possible speciation", and thus did not propose that the Cit+ mutants were a different species, but that speciation might be an eventual consequence of the trait's evolution. Lenski acknowledges that scientists, including him and his team, often use short hand and jargon when discussing speciation, instead of writing more carefully and precisely on the matter, and this can cause issues.
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Many geneticists at the time did little to bridge the gap between the genetics of natural selection and the origin of reproductive barriers between species. Ronald Fisher proposed a model of speciation in his 1930 publication The Genetical Theory of Natural Selection, where he described disruptive selection acting on sympatric or parapatric populations — with reproductive isolation completed by reinforcement. Other geneticists such as J. B. S. Haldane did not even recognize that species were real, while Sewall Wright ignored the topic, despite accepting allopatric speciation. The primary contributors to the incorporation of speciation into modern evolutionary synthesis were Ernst Mayr and Theodosius Dobzhansky.
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Adaptive radiations involve an increase in a clade's speciation rate coupled with divergence of morphological features that are directly related to ecological habits; these radiations involve speciation not driven by geographic factors and occurring in sympatry; they also may be associated with the acquisition of a key trait. Nonadaptive radiations arguably encompass every type of evolutionary radiation that is not an adaptive radiation, although when a more precise mechanism is known to drive diversity, it can be useful to refer to the pattern as, e.g., a geographic radiation. Geographic radiations involve an increase in speciation caused by increasing opportunities for geographic isolation.
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The vicariant populations then undergo genetic changes as they become subjected to different selective pressures, experience genetic drift, and accumulate different mutations in the separated populations gene pools. The barriers prevent the exchange of genetic information between the two populations leading to reproductive isolation. If the two populations come into contact they will be unable to reproduce—effectively speciating. Other isolating factors such as population dispersal leading to emigration can cause speciation (for instance, the dispersal and isolation of a species on an oceanic island) and is considered a special case of allopatric speciation called peripatric speciation.
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The majority of species within the genus Cranioleuca diverged relatively recently in a rapid speciation event beginning approximately 3.5 Ma. It is unclear what drove the divergence, as there is little difference in morphology or behaviour between species. One hypothesis is that a rapid change in plumage, in conjunction with some other traits, may have caused reproductive isolation and speciation. There is evidence that climatic niches have been a driver of speciation within the genus, particularly within the line-cheeked spinetail species complex. Its distribution spans an elevation gradient, as well as different climates, which is reflected in gradual phenotypic differences.
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The most significant and rapid genetic reorganization occurs in extremely small populations that have been isolated (as on islands). His theory of peripatric speciation (a more precise form of allopatric speciation which he advanced), based on his work on birds, is still considered a leading mode of speciation, and was the theoretical underpinning for the theory of punctuated equilibrium, proposed by Niles Eldredge and Stephen Jay Gould. Mayr is sometimes credited with inventing modern philosophy of biology, particularly the part related to evolutionary biology, which he distinguished from physics due to its introduction of (natural) history into science.
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Pseudoextinction is an event that occurs much more frequently under the assumption of a Phyletic gradualism model of evolution, under which speciation is slow, uniform and gradual. The majority of speciation would occur through anagenesis under this model, resulting in a majority of species undergoing Pseudoextinction. However, the model of punctuated equilibrium is more widely accepted, with the proposal that most species remain in stasis, a state of very little evolutionary change, for a large proportion of the species' lifespan. This would result in increased cases of speciation through cladogenesis and true extinction, with fewer cases of Pseudoextinction.
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2005 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase. Most polyploids display heterosis relative to their parental species, and may display novel variation or morphologies that may contribute to the processes of speciation and eco-niche exploitation. The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels. Many of these rapid changes may contribute to reproductive isolation and speciation.
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The result of four billion years of evolution is the diversity of life around us, with an estimated 1.75 million different species in existence today. Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within human life-spans are rare. However speciation has been observed in present-day organisms, and past speciation events are recorded in fossils. Scientists have documented the formation of five new species of cichlid fishes from a single common ancestor that was isolated fewer than 5,000 years ago from the parent stock in Lake Nagubago.
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Mathematical models, laboratory studies, and observational evidence supports the existence of parapatric speciation's occurrence in nature. The qualities of parapatry imply a partial extrinsic barrier during divergence; thus leading to a difficulty in determining whether this mode of speciation actually occurred, or if an alternative mode (notably, allopatric speciation) can explain the data. This problem poses the unanswered question as to its overall frequency in nature. Parapatric speciation can be understood as a level of gene flow between populations where m=0 in allopatry (and peripatry), m=0.5 in sympatry, and midway between the two in parapatry.
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While the traditional model of paleontology, the phylogenetic model, posits that features evolved slowly without any direct association with speciation, the relatively newer and more controversial idea of punctuated equilibrium claims that major evolutionary changes don't happen over a gradual period but in localized, rare, rapid events of branching speciation. Punctuated gradualism is considered to be a variation of these models, lying somewhere in between the phyletic gradualism model and the punctuated equilibrium model. It states that speciation is not needed for a lineage to rapidly evolve from one equilibrium to another but may show rapid transitions between long-stable states.
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Hybridization may be important in speciation in some plant groups. However, homoploid hybrid speciation (not increasing the number of sets of chromosomes) may be rare: by 1997, only 8 natural examples had been fully described. Experimental studies suggest that hybridization offers a rapid route to speciation, a prediction confirmed by the fact that early generation hybrids and ancient hybrid species have matching genomes, meaning that once hybridization has occurred, the new hybrid genome can remain stable. Many hybrid zones are known where the ranges of two species meet, and hybrids are continually produced in great numbers.
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Polyploidy is usually fatal in animals where extra chromosome sets upset fetal development, but is often found in plants. A form of hybrid speciation that is relatively common in plants occurs when an infertile hybrid becomes fertile after doubling of the chromosome number. Hybridization without change in chromosome number is called homoploid hybrid speciation. This is the situation found in most animal hybrids.
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The mass extinction created many open niches for Antarctic notothenioids to colonize, triggering adaptive radiation. It was originally thought that AFGPs triggered radiation but further research in the timing of AFGP onset and speciation did not support the theory. AFGPs do not fit with the early burst model because they were developed in Antarctic fish 10 Ma before rapid speciation.
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A demographic expansion following the last glacial maximum (20,000 years ago) is thought to have led to the allopatric speciation of the southern tigrina.
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Geoderma, 71–85.Nacht, D. M., & al., e. (2004). Atmospheric Mercury Emissions and Speciation at the Sulphur Bank Mercury Mine Superfund Site, Northern California.
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Morphs often interbreed, but they can also be reproductively isolated and represent genetically distinct populations, which have been cited as examples of incipient speciation.
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As the term character displacement is commonly used, it generally refers to morphological differences due to competition. Brown and Wilson viewed character displacement as a phenomenon involved in speciation, stating, "we believe that it is a common aspect of geographical speciation, arising most often as a product of the genetic and ecological interaction of two (or more) newly evolved, cognate species [derived from the same immediate parental species] during their period of first contact." While character displacement is important in various scenarios of speciation,Thierry Lodé "La guerre des sexes chez les animaux" 2006 Eds Odile jacob, Paris including adaptive radiations like the cichlid fish faunas in the rift lakes of East Africa, it also plays an important role in structuring communities. It also plays a role in speciation by reinforcement in such that allopatric populations overlapping in sympatry exhibit greater trait divergence.
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Short, Lester L., and Jennifer F. Horne. "A Review of Duetting, Sociality and Speciation In Some African Barbets (Capitonidae)." Condor 85.3 (1983): 323-32. Web.
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The biogeochemistry of cadmium and its release to the environment has been the subject of review, as has the speciation of cadmium in the environment.
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The debate now turns to how often sympatric speciation may actually occur in nature and how much of life's diversity it may be responsible for.
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Much of the work characterizing subquinaria- recens speciation is built on a body of work initiated in the 1970s by John Jaenike and fellow researchers.
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Islands are attractive sites for ecological research because they provide clear examples of evolution in action. They show interesting patterns of colonization, adaptation, and speciation.
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This leads to speciation, such as the indigo bird, which is suggested by the fact they have a more recent evolutionary origin than their hosts.
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Short, Lester L., and Jennifer F. Horne. "A Review of Duetting, Sociality and Speciation In Some African Barbets (Capitonidae)." Condor 85.3 (1983): 323-32. Web.
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Cryptic species of ground wētā (Hemiandrus maculifrons complex) are host to different lineages of Wolbachia which might explain their speciation without ecological or geographical separation.
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Sympatric speciation suggested by monophyly of crater lake cichlids. Nature 368(6472): 629-632. The outflow is impassable to most fishes because of a waterfall.
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Their relationship to other groups of Satyrine butterflies and their complex patterns of speciation within and among mountain ranges have led to several biogeographic discussions.
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In biology, saltation (from Latin, saltus, "leap") is a sudden and large mutational change from one generation to the next, potentially causing single- step speciation. This was historically offered as an alternative to Darwinism. Some forms of mutationism were effectively saltationist, implying large discontinuous jumps. Speciation, such as by polyploidy in plants, can sometimes be achieved in a single and in evolutionary terms sudden step.
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This is important in sympatric speciation because species with similar males may be competing for the same females. There may be a fitness advantage for one phenotype that could allow one species to invade another. Studies show this effect in species that are genetically similar, have the capability to interbreed, and show phenotypic color variation. Ecological character displacement is another means for sympatric speciation.
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The burden now lies on providing evidence for sympatric divergence occurring in non-isolated habitats. It is not known how much of the earth's diversity it could be responsible for. Some still say that panmixia should slow divergence, and thus sympatric speciation should be possible but rare (1). Meanwhile, others claim that much of the earth's diversity could be due to speciation without geographic isolation.
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Over time, survivor species of the holly genus adapted to different ecological niches. This led to reproductive isolation, an example of ecological speciation. In the Pliocene, around five million years ago, mountain formation diversified the landscape and provided new opportunities for speciation within the genus. The fossil record indicates that the Ilex lineage was already widespread prior to the end of the Cretaceous period.
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Reticulation affects survival, fitness and speciation rates of species. Reticulate evolution can happen between lineages separated only for a short time, for example through hybrid speciation in a species complex. Nevertheless, it also takes place over larger evolutionary distances, as exemplified by the presence of organelles of bacterial origin in eukaryotic cells. Reticulation occurs at various levels:Perez, Julio E; Alfonsi, Carmen; Munoz, Carlos. (2010).
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Ice ages have played important roles in facilitating speciation among vertebrate species. This concept of refugia has been applied to numerous groups of species and their biogeographic distributions. Glaciation and subsequent retreat caused speciation in many boreal forest birds, such as with North American sapsuckers (Yellow-bellied, Red-naped, and Red-breasted); the warblers in the genus Setophaga (S. townsendii, S. occidentalis, and S. virens), Oreothlypis (O.
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April 30, 2014. Accessed February 14, 2018. The separation of the sockeye and the kokanee created a unique example of sympatric speciation that is relatively new in evolutionary terms. While they occupy the same areas and habitats during the breeding season, when ocean-going sockeye salmon return to freshwater to spawn, the two populations do not mate with each other in some regions, suggesting speciation.
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The high species diversity of the subtribe Pronophilina has inspired multiple theories about speciation and diversification processes. Páramo-dwellers might represent ancient or relictual taxa from open low-land biomes that were isolated by the up-lifting of the Andes, or they might be the result of recent radiation due to specialization and isolation.Adams, Michael J. (1985). "Speciation in the pronophiline butterflies (Satyridae) of the northern Andes".
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According to the modern definition, the evolutionary transition from the ancestral to the daughter species is microevolutionary, because it results from selection (or, more generally, sorting) among varying organisms. However, speciation has also a macroevolutionary aspect, because it produces the interspecific variation species selection operates on. Another macroevolutionary aspect of speciation is the rate at which it successfully occurs, analogous to reproduction success in microevolution.
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Everything fitted in to the new framework, except "heretics" like Richard Goldschmidt who annoyed Mayr and Dobzhansky by insisting on the possibility of speciation by macromutation, creating "hopeful monsters". The result was "bitter controversy". Speciation via polyploidy: a diploid cell may fail to separate during meiosis, producing diploid gametes which self- fertilize to produce a fertile tetraploid zygote that cannot interbreed with its parent species.
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The origin of current-day species is not fully understood so far, but one hypothesis suggests that ecological differences, notably in the adaptation to an aquatic lifestyle, may have evolved between populations and led to parapatric speciation. Alternatively, the complex geological history of the Balkan peninsula may have further separated populations there, with subsequent allopatric speciation and the spread of species into their current ranges.
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Drosophila pseudoobscura is a species of fruit fly, used extensively in lab studies of speciation. It is native to western North America. In 2005, D. pseudoobscura was the second Drosophila species to have its genome sequenced, after the model organism Drosophila melanogaster. Allopatric speciation has been induced by reproductive isolation in D. pseudoobscura after only eight generations using different food types, starch and maltose.
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The traditional classification is considered by some researchers to be obsolete, while others argue for its merits. Proponents of non-geographic schemes often justify non-geographic classifications, not by rejection of the importance of reproductive isolation (or even the processes themselves), but instead by the fact that it simplifies the complexity of speciation. One major critique of the geographic framework is that it arbitrarily separates a biological continuum into discontinuous groups. Another criticism rests with the fact that, when speciation is viewed as a continuum of gene flow, parapatric speciation becomes unreasonably represented by the entire continuum—with allopatric and sympatric existing in the extremes.
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A source of confusion in determining the exact age of the Pan–Homo split is evidence of a more complex speciation process rather than a clean split between the two lineages. Different chromosomes appear to have split at different times, possibly over as much as a 4-million-year period, indicating a long and drawn out speciation process with large-scale hybridization events between the two emerging lineages as recently as 6.3 to 5.4 million years ago according to Patterson et al. (2006). Speciation between Pan and Homo occurred over the last 9 million years. Ardipithecus probably branched off of the Pan lineage in the middle Miocene Messinian.
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In 1995, D. H. Erwin, et al. published a major work—New Approaches to Speciation in the Fossil Record—which compiled 58 studies of fossil speciation (between 1972 and 1995) finding most of the examples suggesting stasis (involving anagenesis or punctuation) and 16 studies suggesting speciation. Despite stasis appearing to be the predominate conclusion at first glance, this particular meta-study investigated deeper, concluding that, "...no single pattern appears dominate..." with "...the preponderance of studies illustrating both stasis and gradualism in the history of a single lineage". Many of the studies conducted utilize seafloor sediments that can provide a significant amount of data concerning planktonic microfossils.
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The binary state speciation and extinction model (BiSSE) is a discrete-space model that does not directly follow the framework of those mentioned above. It allows estimation of ancestral binary character states jointly with diversification rates associated with different character states; it may also be straightforwardly extended to a more general multiple-discrete-state model. In its most basic form, this model involves six parameters: two speciation rates (one each for lineages in states 0 and 1); similarly, two extinction rates; and two rates of character change. This model allows for hypothesis testing on the rates of speciation/extinction/character change, at the cost of increasing the number of parameters.
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However, there is no fundamental distinction between these processes; small changes compound over time and eventually lead to speciation. Creationists argue that a finite number of discrete kinds were created, as described in the Book of Genesis, and these kinds determine the limits of variation. Early Creationists equated kinds with species, but most now accept that speciation can occur: not only is the evidence overwhelming for speciation, but the millions of species now in existence could not have fit in Noah's Ark, as depicted in Genesis. Created kinds identified by creationists are more generally on the level of the family (for example, Canidae), but the genus Homo is a separate kind.
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"Species selection operates on variation provided by the largely random process of speciation and favors species that speciate at high rates or survive for long periods and therefore tend to leave many daughter species." Species selection comprises (a) effect-macroevolution, where organism-level traits (aggregate traits) affect speciation and extinction rates (Stanley’s original concept), and (b) strict-sense species selection, where species-level traits (e.g. geographical range) affect speciation and extinction rates. It has been argued that effect macroevolution is reducible to microevolution because both operate through selection on organismic traits, but Grantham demonstrated that effect macroevolution can oppose selection at the organismic level and is therefore not reducible microevolution.
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In human evolution, incomplete lineage sorting is used to diagram hominin lineages that may have failed to sort out at the same time that speciation occurred in prehistory. Due to the advent of genetic testing and genome sequencing, researchers found that the genetic relationships between hominin lineages might disagree with previous understandings of their relatedness based on physical characteristics. Moreover, divergence of the last common ancestor (LCA) may not necessarily occur at the same time as speciation. Lineage sorting is a method that allows paleoanthropologists to explore the genetic relationships and divergences that may not fit with their previous speciation models based on phylogeny alone.
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He has written extensively on speciation, adaptive radiation, and determinants of diversity in several plant groups, including Bromeliaceae, Rapateaceae, Orchidaceae as well as the Hawaiian lobeliads.
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Polyploidization may lead to speciation because the reproductive isolation may develop between hexaploid and either tetraploid or diploid due to the mistake of alignment during meiosis.
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Futuyma's research examines speciation and population biology, particularly the evolutionary interactions between herbivorous insects and their plant hosts and the implications for evolution of host specificity.
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Additional classifications of paralogs include alloparalogs (out-paralogs) and symparalogs (in-paralogs). Alloparalogs are paralogs that evolved from gene duplications that preceded the given speciation event.
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In particular, if the trait is quantitative and univariate then both higher and lower trait levels are favoured. Disruptive selection can be a precursor to speciation.
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Beresford, P. & Cracraft, J. (1999). Speciation in African forest robins (Stiphrornis): species limits, phylogenetic relationships, and molecular biogeography. American Museum Novitates 3270: 1–22. PDF available.
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Beresford, P. & Cracraft, J. (1999). Speciation in African forest robins (Stiphrornis): species limits, phylogenetic relationships, and molecular biogeography. American Museum Novitates 3270: 1–22. PDF available.
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Carlquist, S. (1979). Stylidium in Arnhem Land: New species, modes of speciation on the sandstone plateau, and comments on floral mimicry. Aliso, 9(3): 411-461.
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Dobzhansky, a geneticist, published Genetics and the Origin of Species in 1937, in which he formulated the genetic framework for how speciation could occur. He recognized that speciation was an unsolved problem in biology at the time, rejecting Darwin's position that new species arose by occupation of new niches — contending that reproductive isolation was instead based on barriers to gene flow. Subsequently, Mayr conducted extensive work on the geography of species, emphasizing the importance of geographic separation and isolation, in which he filled Dobzhansky's gaps concerning the origin of biodiversity (in his 1942 book). Both of their works gave rise, not without controversy, to the modern understanding of speciation; stimulating a wealth of research on the topic. Furthermore, this extended to plants as well as animals with G. Ledyard Stebbins’s book, Variation and Evolution in Plants and the much later, 1981 book, Plant Speciation by Verne Grant.
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Biological journal of the Linnean Society. Vol. 97, no. 3. pp. 594-603. Saltational speciation has been recognized in the genus Clarkia (Lewis, 1966).Lewis, H. (1966).
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It states that speciation is not needed for a lineage to rapidly evolve from one equilibrium to another but may show rapid transitions between long-stable states.
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Salsifies are one example where hybrid speciation has been observed.Ownbey, M. 1950. Natural hybridization and amphiploidy in the genus Tragopogon. American Journal of Botany 37:487-499.
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Data about the presence or absence of species on various continents and islands (biogeography) can provide evidence of common descent and shed light on patterns of speciation.
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Mesungulatidae is an extinct clade of meridiolestidan dryolestoid mammals from the Late Cretaceous of South America. They are particularly notable for their ecological speciation and large size.
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Her other research areas include the nature and scale of recombination and mutation rate variation across genomes, the genetics of aquatic invasions, and speciation in ancient lakes.
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It has been suggested that the dusky-billed parrotlet is basal to all other species of the genus Forpus based on diversification and speciation rates and patterns.
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Hohenlohe, Paul, A.; Arnold, Stevan J. 2010. “The dimensionality of mate choice, sexual isolation and speciation” Proceedings of the National Academy of Sciences U.S.A. 107: 16583-165588.
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The chemistry of concentrated solutions under ionizing radiation is extremely complex. Radiolysis can locally modify redox conditions, and therefore the speciation and the solubility of the compounds.
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Sympatric speciation events are quite common in plants, which are prone to acquiring multiple homologous sets of chromosomes, resulting in polyploidy. The polyploid offspring occupy the same environment as the parent plants (hence sympatry), but are reproductively isolated. A number of models have been proposed for alternative modes of sympatric speciation. The most popular, which invokes the disruptive selection model, was first put forward by John Maynard Smith in 1966.
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In the seventh chapter, Dobzhansky discusses polyploidy, a condition (common in plants) where an organism has more than two complete sets of chromosomes. (Humans are diploid, having one set each from the mother and father.) He discusses case histories such as that of Raphanobrassica, a hybrid between the radish and the cabbage. This is an example of "cataclysmic" speciation, an exception to his general rule that speciation is a slow process.
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Hemipenes are also being used to study speciation among squamata, especially in identifying cryptic diversity and understanding taxonomy at a species level. One study conducted in 2015 investigated anole speciation through hemipenis variation, and found that anole hemipenial morphology evolved six times faster than other non-genital morphological features. Such studies can help researchers understand adaptive radiation and recover phylogenetic relationships, especially between species that are morphologically very similar.
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"Sympatric Speciation and Darwin's Finches". In D. Otte & J. A. Endler (eds.) Speciation and its consequences. Sinauer. However, further work showed that "the choice of a male by a female is independent of any conditioning influence of her father's song type and there is no evidence of assortative mating by bill type... Hence there is no direct evidence of reproductive subdivision in the population".Grant, B. Rosemary; Grant, Peter R. 1989.
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Allopatric speciation begins when a population becomes geographically separated. Geological processes, such as the emergence of mountain ranges, the formation of canyons, or the flooding of land bridges by changes in sea level may result in separate populations. For speciation to occur, separation must be substantial, so that genetic exchange between the two populations is completely disrupted. In their separate environments, the genetically isolated groups follow their own unique evolutionary pathways.
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Female choice might actually be the selection pressure that drove the divergence of male signal frequency in the E. binotata species complex. Male signals of the different species within the Enchenopa binotata complex Cocroft, R. B., Rodríguez, R. L., & Hunt, R. E. (2008). Host shifts, the evolution of communication, and speciation in the Enchenopa binotata species complex of treehoppers. Specialization, speciation, and radiation: the evolutionary biology of herbivorous insects, 88-100.
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This results in isolation of breeding populations of D. pilirostris and notable sub-speciation among the Himizu Hime which is not found among the standard Japanese shrew moles.
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Carlquist, S.J. (1979). Stylidium in Arnhem land: New species, modes of speciation on the sandstone plateau, and comments on floral mimicry. Aliso, 9: 411-461.Coleman, Helen. (1998).
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They evolved in the same geographic region, making the parasite–host pair an example of sympatric speciation. The species is the first inquiline known among the lower attines.
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Similarly, full analytical approaches have been proposed and applied to determine which speciation mode a species underwent in the past using various approaches or combinations thereof: species-level phylogenies, range overlaps, symmetry in range sizes between sister species pairs, and species movements within geographic ranges. Molecular clock dating methods are also often employed to accurately gauge divergence times that reflect the fossil or geological record (such as with the snapping shrimp separated by the closure of the Isthmus of Panama or speciation events within the genus Cyclamen). Other techniques used today have employed measures of gene flow between populations, ecological niche modelling (such as in the case of the Myrtle and Audubon's warblers or the environmentally-mediated speciation taking place among dendrobatid frogs in Ecuador), and statistical testing of monophyletic groups. Biotechnological advances have allowed for large scale, multi-locus genome comparisons (such as with the possible allopatric speciation event that occurred between ancestral humans and chimpanzees), linking species' evolutionary history with ecology and clarifying phylogenetic patterns.
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There exists evidence for vertebrate speciation despite limitations imposed by the fossil record. Studies have been conducted documenting similar patterns seen in marine invertebrates. For example, extensive research documenting rates of morphological change, evolutionary trends, and speciation patterns in small mammals has significantly contributed to the scientific literature; once more, demonstrating that evolution (and speciation) occurred in the past and lends support common ancestry. A study of four mammalian genera: Hyopsodus, Pelycodus, Haplomylus (three from the Eocene), and Plesiadapis (from the Paleocene) found that—through a large number of stratigraphic layers and specimen sampling—each group exhibited, "gradual phyletic evolution, overall size increase, iterative evolution of small species, and character divergence following the origin of each new lineage".
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Additionally, species with larger ranges may be more likely to undergo allopatric speciation, which would increase rates of speciation (Rosenzweig 2003). The combination of lower extinction rates and high rates of speciation leads to the high levels of species richness in the tropics. A critique of the geographical area hypothesis is that even if the tropics is the most extensive of the biomes, successive biomes north of the tropics all have about the same area. Thus, if the geographical area hypothesis is correct these regions should all have approximately the same species richness, which is not true, as is referenced by the fact that polar regions contain fewer species than temperate regions (Gaston and Blackburn 2000).
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Lucinda P. Lawson maintains that the species' geographic ranges within the Eastern Afromontane Biodiversity Hotspot support a peripatric model that is driving speciation; suggesting that this mode of speciation may play a significant role in "highly fragmented ecosystems". In a study of the phylogeny and biogeography of the land snail genus Monacha, the species M. ciscaucasica is thought to have speciated peripatrically from a population of M. roseni. In addition, M. claussi consists of a small population located on the peripheral of the much larger range of M. subcarthusiana suggesting that it also arose by peripatric speciation. Red spruce (Picea rubens) has arisen from an isolated population of black spruce (Picea mariana).
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Raulings, EJ and Ladiges, PY. (2001). Morphological variation and speciation in Stylidium graminifolium (Stylidiaceae), description of S. montanum and reinstatement of S. armeria. Australian Systematic Botany, 14: 901-935.
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Alexander, R. D., and Bigelow, R. S. 1960. Allochronic speciation in field crickets, and a new species, Acheta veletis. Evolution 14, 334-346. There is one generation per year.
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Ritchie's work has focused on understanding the genetic basis of traits influencing reproductive isolation between species. His work has contributed to our current understanding of Speciation and Sexual selection.
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Atwood, J. L. 1988. Speciation and geographic variation in Black-tailed Gnatcatchers. Ornithol. Monogr. 42 The golden-crowned kinglet has a wingspan of 5.5-7.1 in (14-18 cm).
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Nevo received a M.Sc and PhD (1964) from Hebrew University. His Ph.D thesis was entitled "Population studies of Anurans from the lower Cretaceous of Makhtesh Ramon, Israel". WorldCat item record He founded the Institute of Evolution at Haifa in 1973. Nevo works with many evolutionary subjects, involving understanding and tracking of speciation processes, modifications of highly evolved traits (vision), climatic and geographic effects in sympatric speciation in insects, bacteria, fungi, mammals and crops.
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Coyne and Orr argue that the geographic classification scheme is valuable in that biogeography controls the strength of the evolutionary forces at play, as gene flow and geography are clearly linked. James Mallet and colleagues contend that the sympatric vs. allopatric dichotomy is valuable to determine the degree in which natural selection acts on speciation. Kirkpatrick and Ravigné categorize speciation in terms of its genetic basis or by the forces driving reproductive isolation.
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Complete sourced list of observed instances of speciation, TalkOrigins Archive In creation science, creationists accepted speciation as occurring within a "created kind" or "baramin", but objected to what they called "third level-macroevolution" of a new genus or higher rank in taxonomy. There is ambiguity in the ideas as to where to draw a line on "species", "created kinds", and what events and lineages fall within the rubric of microevolution or macroevolution.
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The more advantageous the trait is the more common it will become in the population. Disruptive selection is a specific type of natural selection that actively selects against the intermediate in a population, favoring both extremes of the spectrum. Disruptive selection is inferred to oftentimes lead to sympatric speciation through a phyletic gradualism mode of evolution. Disruptive selection can be caused or influenced by multiple factors and also have multiple outcomes, in addition to speciation.
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Heliconius butterflies are models for the study of speciation. Hybrid speciation has been hypothesized to occur in this genus and may contribute to the diverse mimicry found in Heliconius butterflies. It has been proposed that two closely related species, H. cydno and H. melpomene, hybridized to create the species H. heurippa. In addition, the clade containing Heliconius erato radiated before Heliconius melpomene, establishing the wing pattern diversity found in both species of butterfly.
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Within each lake there are different niches that a species could occupy. For example, different diets and depth of the water could help to maintain isolation between species in the same lake. Allochrony offers some empirical evidence that sympatric speciation has taken place, as many examples exist of recently diverged (sister taxa) allochronic species. A rare example of sympatric speciation in animals is the divergence of "resident" and "transient" orca forms in the northeast Pacific.
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The German evolutionary biologist Ernst Mayr argued in the 1940s that speciation cannot occur without geographic, and thus reproductive, isolation. He stated that gene flow is the inevitable result of sympatry, which is known to squelch genetic differentiation between populations. Thus, a physical barrier must be present, he believed, at least temporarily, in order for a new biological species to arise. This hypothesis is the source of much controversy around the possibility of sympatric speciation.
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Gene families arose from multiple duplications of an ancestral gene, followed by mutation and divergence. Duplications can occur within a lineage (e.g., humans might have two copies of a gene that is found only once in chimpanzees) or they are the result of speciation. For example, a single gene in the ancestor of humans and chimpanzees now occurs in both species and can be thought of as having been 'duplicated' via speciation.
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The examples described below represent different modes of speciation and provide strong evidence for common descent. It is important to acknowledge that not all speciation research directly observes divergence from "start-to-finish". This is by virtue of research delimitation and definition ambiguity, and occasionally leads research towards historical reconstructions. In light of this, examples abound, and the following are by no means exhaustive—comprising only a small fraction of the instances observed.
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Adaptive radiation is the rapid speciation of multiple species from a common ancestor to fill empty niches. Evidence of adaptive radiation is common ancestry, early bursts of speciation that decrease with time and a correlation between phenotype and environment. The species flock concept is the phenomena of related species sharing the same habitat. A group of species fit the species flock concept if they exhibit species richness, a common ancestor and share the same area.
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In other words, alloparalogs are paralogs that evolved from duplication events that happened in the LCA of the organisms being compared. The example above is an example alloparalogy. Symparalogs are paralogs that evolved from gene duplication of paralogous genes in subsequent speciation events. From the example above, if the descendant with genes A1 and B underwent another speciation event where gene A1 duplicated, the new species would have genes B, A1a, and A1b.
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Diversification rates are the rates at which new species form (the Speciation rate, λ) and living species go extinct (the extinction rate, μ). Diversification rates can be estimated from fossils, data on the species diversity of clades and their ages, or phylogenetic trees. Diversification rates are typically reported on a per-lineage basis (e.g. speciation rate per lineage per unit of time), and refer to the diversification dynamics expected under a birth-death process.
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It is thought that rivers may play a role as the geographic barriers to Charis, not unlike the river barrier hypothesis used to explain the high rates of diversity in the Amazon basin—though this hypothesis has been disputed. Dispersal-mediated allopatric speciation is also thought to be a significant driver of diversification throughout the Neotropics. Allopatric speciation can result from mountain topography. Climatic changes can drive species into altitudinal zones—either valleys or peaks.
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Punctuated equilibrium postulates that evolutionary change is concentrated during a geologically short speciation phase, which is followed by evolutionary stasis that persists until the species goes extinct. The prevalence of evolutionary stasis through most of the existence time of species is a major argument for the relevance of species selection in shaping the evolutionary history of clades. However, punctuated equilibrium is neither a macroevolutionary model of speciation, nor is it a prerequisite for species selection.
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Several factors could be responsible for this diversity: the availability of a multitude of niches probably favored specialization, as few other fish taxa are present in the lakes (meaning that sympatric speciation was the most probable mechanism for initial specialization). Also, continual changes in the water level of the lakes during the Pleistocene (which often turned the largest lakes into several smaller ones) could have created the conditions for secondary allopatric speciation.
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Within this region exists a forest fragment estimated to have been isolated for 1000–3000 years. The population of S. hemimelaena antbirds that reside in the isolated patch express significant song divergence; thought to be an "early step" in the process of peripatric speciation. Further, peripheral isolation "may partly explain the dramatic diversification of suboscines in Amazonia". The montane spiny throated reed frog species complex (genus: Hyperolius) originated through occurrences of peripatric speciation events.
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The different forms mercury exists in (such as elemental mercury vapour, methylmercury, or mercuric chloride) are commonly designated "species". As mentioned above, the main groups of mercury species are elemental mercury, inorganic and organic mercury forms. Speciation is the term commonly used to represent the distribution of a quantity of mercury among various species. Speciation influences the transport of mercury within and between environmental compartments including the atmosphere and oceans, among others.
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This led to reproductive isolation, an example of ecological speciation. In the Pliocene, around five million years ago, the formation of the Southern Alps diversified the landscape and provided new opportunities for speciation within the genus Nestor. Around three million years ago, two lineages adapted to high altitude and low altitude, respectively. The high-altitude lineage gave rise to the modern kea, while the low-altitude lineage gave rise to the various kaka species.
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Jerry Allen Coyne (born December 30, 1949) is an American biologist known for his work on speciation and his commentary on intelligent design. A prolific scientist and author, he has published numerous papers elucidating the theory of evolution. He is currently a professor emeritus at the University of Chicago in the Department of Ecology and Evolution. His concentration is speciation and ecological and evolutionary genetics, particularly as they involve the fruit fly, Drosophila.
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A major taxonomy review in 1974 resulted in 6 species in the genus Aulacorhynchus,Haffer, J. (1974). Avian speciation in tropical South America. Publ. Nuttall Ornithol. Club 14: 1–390.
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Biology Direct 4: 46. Polyploidy (most common in plants but not unknown in animals) is saltational: a significant change (in gene numbers) can result in speciation in a single generation.
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R. C. Hulbert Jr. and G. S. Morgan. 1989. Papers in Florida Paleontology 2.Alroy, J., Speciation and extinction in the fossil record of North American mammals. Ecological Reviews, 2008.
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Futuyma, D. J. 2009. Evolution (2nd edition). Sinauer Associates, Inc. Allopatric speciation is the evolution of species caused by the geographic isolation of two or more populations of a species.
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Hybrid speciation has been observed in various species complexes, such as insects, fungi and plants. In plants, hybridization often takes place through polyploidization, and hybrid plant species are called nothospecies.
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However, a potential mechanism that could promote speciation is that rearrangements reduce gene flow more by suppressing recombination (and extending the effects of linked isolation genes) than by reducing fitness.
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Wing coloration plays a key role in mate choice and has further implications in regards to sympatric speciation. Macrolide scent gland extracts and wing- clicking behavior further characterize this species.
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These rivers were once connected, but are now separated. Also, the environment and temperature of the Nujiang River became greatly different between the northern and southern areas, leading to speciation.
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Divergence of the pheromone composition can result in reproductive isolation and eventual speciation. This evolution is thought to take place in a concerted way between males and females within a population.
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2006 P.D. Dijkstra: Know thine enemy. Intrasexual selection and sympatric speciation in a Lake Victoria cichlid fish. 2006 P. Korsten: Avian sex allocation and ornamental coloration. A study on blue tits.
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Speciation has been implemented using a 2-means clustering algorithm technique designed to allow the splitting of an existing species into two species, by clustering the individuals that initially belonged to the first species into one of the new two species, each one of them containing the agents that are mutually the most similar. Since EcoSim has the capacity to allow speciation events to occur, it is possible to track speciation events throughout a run of the simulation and construct the actual phylogenetic tree. Each agent also possesses several physical characteristics such as: maximum and current ages, minimum age for mating, maximum and current speeds, vision distance, maximum and current levels of energy, and the amount of energy transmitted to the offspring.
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It is speculated that CI can lead to "rapid speciation". When two populations of the same species are infected by two Wolbachia strains A and B, they might be bidirectionally incompatible and crosses between the two populations do not lead to viable offspring. Thus gene flow between these two populations is interrupted, leading to constant segregation in development and, finally, to speciation. The populations develop to a point where incompatibility would be maintained even in absence of Wolbachia.
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They identified how long ago the common ancestor of hybridizing species diverged into two lines, and found that bird and frog species can produce viable hybrids up to twenty million years after speciation. In addition, the researchers showed that mammal species can only produce viable hybrids up to two or three million years after speciation. Wilson et al. (1974) proposes two hypotheses to explain the relatively faster evolution of hybrid inviability in mammals: the Regulatory and the Immunological Hypotheses.
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The strength of natural selection in the wild was greater than expected; the effect of ecological factors such as niche occupation and the significance of barriers to gene flow are all important. The idea that speciation occurs after populations are reproductively isolated has been much debated. In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later.
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The botanist Verne Grant pioneered the field of plant speciation with his research and major publications on the topic. As stated before, many biologists rely on the biological species concept, with some modern researchers utilizing the phylogenetic species concept. Debate exists in the field concerning which framework should be applied in the research. Regardless, reproductive isolation is the primary role in the process of speciation and has been studied extensively by biologists in their respective disciplines.
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Montgomery (2000) discusses the pattern of the fossil record as compared to tectonic shifts in the plates of the Pacific Northwest of America. The (potential) divergence in Onchorhyncus lineages appear to follow the uprising of the Pacific Rim. The climatic and habitat changes that would follow such a geologic event are discussed, in the context of potential stressors leading to adaptation and speciation. One interesting case involving speciation with salmon is that of the kokanee (landlocked) sockeye.
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Diversification rates can be estimated using the information available in phylogenetic trees. To calculate diversification rates, such phylogenetic trees have to include branch lengths. Various methods are available to estimate speciation and extinction rates from phylogenetic trees using both maximum likelihood and Bayesian statistical approaches. One can also use phylogenetic trees to test for changing rates of speciation and/or extinction, both through time and across clades, and to associate rates of evolution with potential explanatory factors.
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From this arises a host of various issues in defining species, defining isolating barriers, measuring reproductive isolation, among others. Nevertheless, verbal and mathematical models, laboratory experiments, and empirical evidence overwhelmingly supports the occurrence of allopatric speciation in nature. Mathematical modeling of the genetic basis of reproductive isolation supports the plausibility of allopatric speciation; whereas laboratory experiments of Drosophila and other animal and plant species have confirmed that reproductive isolation evolves as a byproduct of natural selection.
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This means that over time there is enough of a difference in their Genomes and the way that species genes interact with each other during the developmental stage. Anagenesis can be viewed as the processes of sexual and natural selection, and genetic drift's effect on an evolving species over time. The second process, speciation, is closely associated with cladogenesis. Speciation includes the actual separation of lineages, into two or more new species, from one specified species of origin.
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Based on the expectation that faster rates of microevolution result in faster rates of speciation, these results suggest that faster evolutionary rates in warm climates almost certainly have a strong influence on the latitudinal diversity gradient. More research needs to be done to determine whether or not speciation rates actually are higher in the tropics. Understanding whether extinction rate varies with latitude will also be important to whether or not this hypothesis is supported (Rolland et al. 2014).
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The concept of incomplete lineage sorting has some important implications for phylogenetic techniques. The concept itself is somewhat challenging and relies on persistence of polymorphisms across different speciation events. Suppose two subsequent speciation events occur where the ancient species gives rise to species A, and secondly to species B and C. When studying a single gene, it can contain multiple haplotypes (a polymorphism). A haplotype can be lost or fixed in a species by genetic drift.
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Calculations derived from the neutral theory result in the false conclusion that fish are equidistant to every single evolutionarily ascending species: the same distance from homo sapiens as to snake, and from ox to rabbit, rat, pig and tiger and boar. Calculations using the hypothesis yield results that capture the branching and punctuated nature of speciation, preserve its gradual increasing fractal complexity over time, and are consistent with patterns of speciation deduced from the fossil record.
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Speciation is the gradual process by which species originate. Speciation can be studied from many perspectives, but regardless of the point of view it often requires reproductive isolation between species. In the case of the Orbicella, these species are broadcast spawner corals and release gametes annually in the same evening into the water column. The night of spawning is normally within the warmest month of the year, and five to eight nights after the full moon.
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Their distinct anatomy from Laurasian dromaeosaurids was likely a consequence of the breakup of Pangaea into Gondwana and Laurasia, where the geological isolation of unenlagiines from their relatives resulted in allopatric speciation.
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The 12th edition also included the hundred insect species published separately in ', and omitted a claim which Linnaeus had made in earlier editions, that new species do not form, implicitly allowing speciation.
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Sexual selection, social competition, and speciation. Quart. Rev. Biol. 58(2):155-183. She has noted how sexual selection can trap animals into sexual dimorphisms, to maintain separate sexes in sexual reproduction.
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Rapid speciation and chromosomal evolution in mammals. Proc. Natl. Acad. Sci. USA 74: 3942-3946 Ectopic recombination can occur during both meiosis and mitosis, although it is more likely occur during meiosis.
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Speciation in situ is facilitated by reproductive isolation and changes in the environmental pressures on the local populations. Many regions of high biodiversity or endemism arise from habitats which require unusual adaptations.
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Phylogenetic and phylogeographic analysis of the genus Orestias (Teleostei: Cyprinodontidae) in the southern Chilean Altiplano: the relevance of ancient and recent divergence processes in speciation. Journal of Fish Biology 82, 927–943.
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This isolation resulted in divergence and speciation of E. tennesseensis.Baskauf, C.J., D.E. McCauley, W.G. Eickmeier. (1994). Genetic analysis of a rare and a widespread species of Echinacea (Asteraceae) , "Evolution" 48: 180-188 (abstract).
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Groves, Colin. Speciation and biogeography of Vietnam’s primates. Vietnamese Journal of Primatology (2007) 1, 27-40. Digital copy The species lives in lowland broadleaf forest, with some populations living in forested mountainous areas.
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Eighmy's research focuses on element speciation, environmental chemistry of leaching behavior, spectroscopic surface analysis, applied geochemistry, reactive barriers, reactive transport modeling, environmental microbiology, biofouling, biofilms, sustainability, carbon sequestration, carbon cycling, and recycled materials.
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A study has shown that the two small populations remaining on Isabela Island have begun undergoing speciation and that one or both populations will eventually become extinct due to a lack of interbreeding.
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The wild ancestor of cultivated adzuki bean is probably Vigna angularis var. nipponensis, which is distributed across Japan, Korea, China, Nepal and Bhutan. Speciation between Vigna angularis var. nipponensis and Vigna angularis var.
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When you get large ancestral populations together with closely timed speciation events these different pieces of DNA retain conflicting affiliations. This makes it hard to determine a common ancestor or points of branching.
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Plant Biology 5: 33–41. For example, if a bee went to one flower and pollen was deposited on the far back of her body, but then it flew to another flower where the stigma was more forward (anterior), pollination could not take place. This can result in reproductive isolation from the parental population and new speciation can occur. It is believed that the lever mechanism is a key factor in the speciation, adaptive radiation, and diversity of this large genus.
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The development and spread of antibiotic resistant bacteria provides evidence that evolution due to natural selection is an ongoing process in the natural world. Natural selection is ubiquitous in all research pertaining to evolution, taking note of the fact that all of the following examples in each section of the article document the process. Alongside this are observed instances of the separation of populations of species into sets of new species (speciation). Speciation has been observed in the lab and in nature.
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If a higher rate of molecular evolution causes increased speciation rates, then adaptation and ultimately speciation may occur more quickly in warm environments and in small bodied species, ultimately explaining observed patterns of diversity across body size and latitude. MTE's ability to explain patterns of diversity remains controversial. For example, researchers analyzed patterns of diversity of New World coral snakes to see whether the geographical distribution of species fit within the predictions of MTE (i.e. more species in warmer areas).
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Directional selection occurs most often under environmental changes and when populations migrate to new areas with different environmental pressures. Directional selection allows for fast changes in allele frequency, and plays a major role in speciation. Analysis on QTL effects has been used to examine the impact of directional selection in phenotypic diversification. This analysis showed that the genetic loci correlating to directional selection was higher than expected; meaning directional selection is a primary cause of phenotypic diversification, which leads to speciation.
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Reinforcement assists speciation by selecting against hybrids upon the secondary contact of two separated populations of a species. Reinforcement is a process of speciation where natural selection increases the reproductive isolation (further divided to pre-zygotic isolation and post-zygotic isolation) between two populations of species. This occurs as a result of selection acting against the production of hybrid individuals of low fitness. The idea was originally developed by Alfred Russel Wallace and is sometimes referred to as the Wallace effect.
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Fossil discoveries in palaeontology, advances in population genetics and a global network of scientific research have provided further details into the mechanisms of evolution. Scientists now have a good understanding of the origin of new species (speciation) and have observed the speciation process in the laboratory and in the wild. Evolution is the principal scientific theory that biologists use to understand life and is used in many disciplines, including medicine, psychology, conservation biology, anthropology, forensics, agriculture and other social-cultural applications.
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In 1868, Moritz Wagner was the first to propose the concept of geographic speciation in which he used the term Separationstheorie. Edward Bagnall Poulton, the evolutionary biologist and a strong proponent of the importance of natural selection, highlighted the role of geographic isolation in promoting speciation, in the process coining the term "sympatric speciation" in 1904. Wagner and other naturalists who studied the geographic distributions of animals, such as Karl Jordan and David Starr Jordan, noticed that closely related species were often geographically isolated from one another (allopatrically distributed) which lead to the advocation of the importance of geographic isolation in the origin of species. Karl Jordan is thought to have recognized the unification of mutation and isolation in the origin of new species — in stark contrast to the prevailing views at the time.
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Parallel speciation occurs, for example, in mosquito fish in the Bahamas, where Gambusia fish inhabit "blue holes"—carbonate caves and depressions flooded with water—throughout the islands. Some of the holes contain the piscivorous predator fish Gobiomorus dormitor, while others have no major predators except birds. The authors of the study tested for ecological speciation by measuring three different data sets: morphological data (to test for divergent natural selection), molecular data (to test for "replicated trait evolution in independent populations" with similar phenotypes), and mate-choice trials (to test for reproductive isolation between "ecologically divergent pairs of populations than ecologically similar ones": a by-product resulting from divergent traits). The study allowed for a natural experiment to test the effects of predator- mediated natural selection and its by-product: ecological speciation.
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A population becomes separated by a geographic barrier; reproductive isolation develops, resulting in two separate species. Speciation by vicariance is widely regarded as the most common form of speciation; and is the primary model of allopatric speciation. Vicariance is a process by which the geographical range of an individual taxon, or a whole biota, is split into discontinuous populations (disjunct distributions) by the formation of an extrinsic barrier to the exchange of genes: that is, a barrier arising externally to a species. These extrinsic barriers often arise from various geologic-caused, topographic changes such as: the formation of mountains (orogeny); the formation of rivers or bodies of water; glaciation; the formation or elimination of land bridges; the movement of continents over time (by tectonic plates); or island formation, including sky islands.
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The duetting of L. chaplini and L. undatus is unknown.Short, Lester L., and Jennifer F. Horne. "A Review of Duetting, Sociality and Speciation In Some African Barbets (Capitonidae)." Condor 85.3 (1983): 323-32. Web.
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Burns, J. 2015. Speciation in an insular sand dune habitat: Atrytonopsis (Hesperiidae: Hesperiinae) - mainly from the southwestern United States and Mexico - off the Carolina coast. Journal of the Lepidopterists' Society 69(4):275-292.
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These two indications that predators attacked selectively suggest the possibility of speciation in response to predation, which is often postulated as a potential cause of the rapid diversification of animals in the Early Cambrian.
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Systematics and origin of species. Columbia University Press, New York. p148 Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication of the Origin of Species.
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Each population has the same adaptive value (competitive and dispersal abilities) and resources demand. Local and regional composition represent a balance between speciation or dispersal (which increase diversity), and random extinctions (which decrease diversity).
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This led them to rule out the possibility of recent interbreeding, and conclude that sympatric speciation had occurred. The two species are believed to have diverged around 37,000 years ago, during the late Pleistocene.
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Washington 61.Sehgal, R. N., Hull, A. C., Anderson, N. L., Valkiūnas, G., Markovets, M. J., Kawamura, S., & Tell, L. A. (2006). Evidence for cryptic speciation of Leucocytozoon spp.(Haemosporida, Leucocytozoidae) in diurnal raptors.
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There is a high degree of divergence between the two in mitochondrial DNA and intron sequences. Speciation is likely to have occurred on two ancient islands which later fused to form present-day Hispaniola.
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Phylogenetic analysis of clones of the two types isolated from different generations demonstrated that the S and L types belonged to distinct, co-existing lineages in the population, and might be undergoing incipient speciation.
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They ended up resorting to cockroaches and scolopendra and, due to their much smaller nutritional value, the snakes slowly shrunk their size until they couldn't grow beyond 50 cm - a process known as allopatric speciation.
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A process of colonisation, speciation and extinction has been at play over many millions of years, including recent times. Some species have arrived in human recorded history while others arrived before but are little changed.
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It is considered an endangered species in the Czech Republic. Recent molecular phylogenetic studies have shown regional populations of B. fechtneri to be highly variable genetically, suggesting they might be in the process of speciation.
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Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422.
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Preface to the Third Edition. Evolutionary biologist Ernst Mayr has written that Buch was the first naturalist to suggest geographic speciation, in 1825.Mayr, Ernst. (1998). The Evolutionary Synthesis: Perspectives on the Unification of Biology.
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It is a small species of bat, weighing approximately .Baker, R. J., Bickham, J. W., & Arnold, M. L. (1985). Chromosomal evolution in Rhogeessa (Chiroptera: Vespertilionidae): possible speciation by centric fusions. Evolution, 39(2), 233-243.
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This is one of the most abundant compounds released by forest trees.Geron, C., et al. (2000). A review and synthesis of monoterpene speciation from forests in the United States. Atmospheric Environment 34(11), 1761-81.
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Tarkhnishvili DN (2012) Evolutionary History, Habitats, Diversification, and Speciation in Caucasian Rock Lizards. In: Advances in Zoology Research, Volume 2 (ed. Jenkins OP), Nova Science Publishers, Hauppauge (NY), p.79-120 Komodo dragons and snakes.
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This is significant, because hybrids' mating behavior would relatively quickly isolate itself from its parental species, and eventually form a species itself, as defined by lack of gene flow. His team also hypothesized that along with a mixed inheritance of color and pattern, the hybrids also obtained a mixed preference for mates from their parental species genes. The H. heurippa likely had a genetic attraction for other hybrids, leading to its reproductive isolation and speciation. Although rare, Heliconius butterflies are an example of homoploid hybrid speciation, i.e.
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Allopatric speciation is typically subdivided into two major models: vicariance and peripatric. Both models differ from one another by virtue of their population sizes and geographic isolating mechanisms. The terms allopatry and vicariance are often used in biogeography to describe the relationship between organisms whose ranges do not significantly overlap but are immediately adjacent to each other—they do not occur together or only occur within a narrow zone of contact. Historically, the language used to refer to modes of speciation directly reflected biogeographical distributions.
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This group of approximately 7,000 islands is prone to speciation and is a great location to study phylogeopgraphy. It was formed around 30-35 million years ago and lead to the evolution of different subspecies of Otus megalotis. The expansion and contraction of biomes during the last glaciation period as well as the profound topography in that area lead to isolation of individuals which evetually caused speciation. There are seven Otus species in the Philippines, 5 of which are endemic to islands among the archipelago.
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Nonadaptive radiations are a subset of evolutionary radiations (or species flocks) that are characterized by diversification that is not driven by resource partitioning. The species that are a part of a nonadaptive radiation will tend to have very similar niches, and in many (though not all) cases will be morphologically similar. Nonadaptive radiations are driven by nonecological speciation. In many cases, this nonecological speciation is allopatric, and the organisms are dispersal-limited such that populations can be geographically isolated within a landscape with relatively similar ecological conditions.
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Speciation requires a degree of reproductive isolation—that is, a reduction in gene flow. However, it is intrinsic to the concept of a species that hybrids are selected against, opposing the evolution of reproductive isolation, a problem that was recognised by Darwin. The problem does not occur in allopatric speciation with geographically separated populations, which can diverge with different sets of mutations. E. B. Poulton realized in 1903 that reproductive isolation could evolve through divergence, if each lineage acquired a different, incompatible allele of the same gene.
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The genomes of homoploid hybrid species are mosaics of the parent genomes as ancestry tracts from the parent species are broken up by recombination. In the case of polyploid hybrid speciation, hybridisation is associated with genome duplication, resulting in an allopolyploid with increased ploidy compared to their parental taxa. In contrast to allopolyploids, autopolyploids are characterised by genome duplication within the same species and are thus not discussed further in the context of this review. Allopolyploid speciation is more common in plants than in animals.
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Additionally, they hypothesized that this rapid mode of speciation seen in Clarkia was analogous to a mode of speciation known as quantum evolution: > Several diploid species of Clarkia (Onagraceae) have very limited areas of > distribution (Lewis and Lewis, 1955). Most of these grow adjacent to or are > surrounded by other closely related species that resemble them so closely > that they would ordinarily be regarded as conspecific. Specific status is > accorded to them because of reproductive isolation coupled with at least one > consistent difference in external morphology.
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Intrinsic to this, parapatry covers the entire continuum; represented as 0 < m < 0.5. Some biologists reject this delineation, advocating the disuse of the term "parapatric" outright, "because many different spatial distributions can result in intermediate levels of gene flow". Others champion this position and suggest the abandonment of geographic classification schemes (geographic modes of speciation) altogether. Natural selection has been shown to be the primary driver in parapatric speciation (among other modes), and the strength of selection during divergence is often an important factor.
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When only one species inhabits a lake, that fish displays an intermediate morphology. Studies on other fish species have shown similar patterns of selection for benthic and limnetic morphologies, which can also lead to sympatric speciation.
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Studies of reinforcement in nature often prove difficult, as alternative explanations for the detected patterns can be asserted. Nevertheless, empirical evidence exists for reinforcement occurring across various taxa and its role in precipitating speciation is conclusive.
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Wagner, Bôhme, Pauwels & Schmitz (2009). A review of the African red–flanked skinks of the Lygosoma fernandi (BURTON, 1836) species group (Squamata: Scincidae) and the role of climate change in their speciation. Zootaxa 2050: 1-30.
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London: John Murray. 5th edition, p. 551. Thus punctuationism in general is consistent with Darwin's conception of evolution. According to early versions of punctuated equilibrium, "peripheral isolates" are considered to be of critical importance for speciation.
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Economic Geology, 44, 13-23.Roqué-Rosell, J., Villanova-de-Benavent, C., Proenza, J.A., Tauler, E. and Galí,S. (2011) Distribution and speciation of Ni in sepiolite- falcondoite-type “garnierite” by EXAFS. Macla, 15, 183-184.
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Moon H.P. 1976. Henry Walter Bates FRS 1825–1892: Explorer, Scientist and Darwinian. Leicestershire Museums, Leicester. Field and experimental work on these ideas continues to this day; the topic connects strongly to speciation, genetics and development.
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The third Pelodytes species, the Caucasian parsley frog (P. caucasicus Boulenger, 1896), is spatially set apart with its distribution in the Caucasus and Turkey. This may be an example of allopatric speciation in ice age refugia.
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There were no particular biotic factors involved, but there was sufficient variation among the founding birds to encourage speciation, and the assortment of genes that the birds received was later undisturbed by further inflow of alien genes.
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This theory has been the subject of debate. Scientists are still skeptical of whether or not this theory is legitimate. Genetic evidence suggests speciation had occurred in certain taxa 1–2 million years ago, preceding the Pleistocene.
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Phyletic gradualism is a model of evolution which theorizes that most speciation is slow, uniform and gradual.Eldredge, N. and S. J. Gould (1972). "Punctuated equilibria: an alternative to phyletic gradualism" In T.J.M. Schopf, ed., Models in Paleobiology.
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Robertson, A., Rich, T.C., Allen, A.M., Houston, L., Roberts, C.A.T., Bridle, J.R., Harris, S.A. and Hiscock, S.J., 2010. Hybridization and polyploidy as drivers of continuing evolution and speciation in Sorbus. Molecular Ecology, 19(8), pp.1675-1690.
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Organoarsenic compounds may pose significant health hazards, depending on their speciation. Arsenous acid (As(OH)3) has an LD50 of 34.5 mg/kg (mice) whereas for the betaine (CH3)3As+CH2CO2− the LD50 exceeds 10 g/kg.
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Science, vol. 339, no. 6115, pp. 74-78. Advancements in molecular biology and theory of evolution within zoological research has unraveled questions concerning speciation events and has expanded phylogenic relationships amongst taxa.Taylor, E. B., McPhail, J.D., 1998.
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Synchronous spawning may form hybrids and is perhaps involved in coral speciation. The immediate cue is most often sunset, which cues the release. The spawning event can be visually dramatic, clouding the usually clear water with gametes.
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When speciation does occur as different lineages branch off and cease to interbreed, a core group may continue to be defined as the original species. The evolution of this group, without extinction or species selection, is anagenesis.
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His most prominent achievement was the development of pseudopolarography, the method that enables the speciation of metal ions at trace concentrations. He published more than 250 papers in international scientific journals and numerous scientific and technical reports.
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Bandel K. (2000). "Speciation among the Melanopsidae (Caenogastropoda). Special emphasis to the Melanopsidae of the Pannonian Lake at Pontian time (Late Miocene) and the Pleistocene and Recent of Jordan". Mitt. Geol.-Paläont. Inst. Univ. Hamburg, Heft 84.
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Charles Darwin in 1868 The scientific study of speciation — how species evolve to become new species — began around the time of Charles Darwin in the middle of the 19th century. Many naturalists at the time recognized the relationship between biogeography (the way species are distributed) and the evolution of species. The 20th century saw the growth of the field of speciation, with major contributors such as Ernst Mayr researching and documenting species' geographic patterns and relationships. The field grew in prominence with the modern evolutionary synthesis in the early part of that century.
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David Starr Jordan reiterated Wagner's proposal in 1905, providing a wealth of evidence from nature to support the theory, and asserting that geographic isolation is obvious but had been unfortunately ignored by most geneticists and experimental evolutionary biologists at the time. Joel Asaph Allen suggested the observed pattern of geographic separation of closely related species be called "Jordan's Law" (or Wagner's Law). Despite the contentions, most taxonomists did accept the geographic model of speciation. Many of the early terms used to describe speciation were outlined by Ernst Mayr.
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Later, population genetic and quantitative genetic studies were conducted showing that completely unfit hybrids lead to an increase in pre-zygotic isolation. After Dobzhansky's idea rose to the forefront of speciation research, it garnered significant support—with Dobzhansky suggesting that it illustrated the final step in speciation (e.g. after an allopatric population comes into secondary contact). In the 1980s, many evolutionary biologists began to doubt the plausibility of the idea, based not on empirical evidence, but largely on the growth of theory that deemed it an unlikely mechanism of reproductive isolation.
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Macroevolution is guided by sorting of interspecific variation ("species selection"), as opposed to sorting of intraspecific variation in microevolution. Species selection may occur as (a) effect-macroevolution, where organism-level traits (aggregate traits) affect speciation and extinction rates, and (b) strict-sense species selection, where species-level traits (e.g. geographical range) affect speciation and extinction rates. Macroevolution does not produce evolutionary novelties, but it determines their proliferation within the clades in which they evolved, and it adds species-level traits as non-organismic factors of sorting to this process.
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Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote. Polyploidy is frequent in plants, some estimates suggesting that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes. Huge explosions in angiosperm species diversity appear to have coincided with the timing of ancient genome duplications shared by many species. It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.
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The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels. Many of these rapid changes may contribute to reproductive isolation and speciation. However seed generated from interploidy crosses, such as between polyploids and their parent species, usually suffer from aberrant endosperm development which impairs their viability, thus contributing to polyploid speciation. Some plants are triploid.
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Speciation has been observed to be a possible consequence of sexual coercion. In diving beetle species family Dytiscidae, an intersexual arms race occurs between males and females. Males have evolved suction cup structures on their forelegs to help grasp females; females have counter-evolved setose dorsal furrows to impede forceful copulation. This continuous evolution (in both the forward and reverse directions) has led to the recent speciation of A. japonicus and A. kishii, where females of A. kishii have lost their dorsal furrows while those of A. japonicus have not.
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The difficulty in supporting a sympatric speciation hypothesis has always been that an allopatric scenario could always be invented, and those can be hard to rule out – but with modern molecular genetic techniques can be used to support the theory. In 2015 Cichlid fish from a tiny volcanic crater lake in Africa were observed in the act of sympatric speciation using DNA sequencing methods. A study found a complex combination of ecological separation and mate-choice preference had allowed two ecomorphs to genetically separate even in the presence of some genetic exchange.
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Two or more taxa that were once considered conspecific (of the same species) may later be subdivided into infraspecific taxa (taxa within a species, such as bacterial strains or plant varieties), that is complex but it is not a species complex. A species complex is in most cases a monophyletic group with a common ancestor, but there are exceptions. It may represent an early stage after speciation but may also have been separated for a long time period without evolving morphological differences. Hybrid speciation can be a component in the evolution of a species complex.
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Changes in chromosome number can play a key role in speciation, as differing chromosome numbers can serve as a barrier to reproduction in hybrids. Human chromosome 2 was created from a fusion of two chimpanzee chromosomes and still contains central telomeres as well as a vestigial second centromere. Polyploidy, especially allopolyploidy, which occurs often in plants, can also result in reproductive incompatibilities with parental species. Agrodiatus blue butterflies have diverse chromosome numbers ranging from n=10 to n=134 and additionally have one of the highest rates of speciation identified to date.
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Another example is in skinks, where the genus Plestiodon (formerly Eumeces) has a complex evolutionary history with ecological speciation and parallel speciation of the three species (within two morphotypes): P. skiltonianus and P. lagunensis, and P. gilberti. P. gilberti occupies dry, low-elevation habitats, and has a larger body size and uniform, solid color scales. The other two species inhabit higher-elevation regions, have smaller bodies, and exhibit colored stripes. The members of the group have similar phenotypic stages during early development but differ in their morphology in later stages.
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The theory assumes that speciation rates are constant with area, and a lower extinction rate coupled with higher speciation leads to more species. The species-area relationship has often been applied to conservation, often quantitatively. The simplest and most commonly used formula was first published by Frank W. Preston. The number of species present in a given area increases in relationship to that area with the relationship S = cAz where S is the number of species, A is the area, and c and z are constants which vary with the system under study.
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Understanding dispersal is an important mechanism that may underlie the body size-species richness pattern. Mainly, dispersal ability can affect speciation rates in various ways: if an organism is capable of dispersing across great distances which span variable habitat, it will be more likely that individuals that settle in these new areas will be subject to different selection regimes, leading to new species through natural selection. Alternatively, great dispersal ability can act against the efforts of natural selection by facilitating geneflow. Thus, species with greater dispersal ability may in fact have lower speciation rates.
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Gottlieb researched a broad array of subjects including plant systematics, plant speciation (Quantum Speciation), polyploidy, gene duplication, biochemical evolution of isozymes and molecular genetics, and published more than 120 research papers and received a number of awards including a John Simon Guggenheim Fellowship (1975), and Fellowship of the American Association for the Advancement of Science (1985). In 1993 he was named Alumni Association Fellow of Oregon State University. In 1965 he earned his master's degree and wrote a thesis on hybridization between species of manzanita in southwestern Oregon.
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The model then uses birth, death, immigration, extinction and speciation to modify community composition over time. ;Hubbell's theta The UNTB model produces a dimensionless "fundamental biodiversity" number, θ, which is derived using the formula: : θ = 2Jmv where: : Jm is the size of the metacommunity (the outside source of immigrants to the local community) :v is the speciation rate in the model Relative species abundances in the UNTB model follow a zero-sum multinomial distribution.Hubbell, S. P.; Lake J. 2003. "The neutral theory of biogeography and biodiversity: and beyond".
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Allopatric speciation has resulted in many of the biogeographic and biodiversity patterns found on Earth: on islands, continents, and even among mountains. Islands are often home to species endemics—existing only on an island and nowhere else in the world—with nearly all taxa residing on isolated islands sharing common ancestry with a species on the nearest continent. Not without challenge, there is typically a correlation between island endemics and diversity; that is, that the greater the diversity (species richness) of an island, the greater the increase in endemism. Increased diversity effectively drives speciation.
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Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity within the populations, by modifying the allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to constrain speciation by combining the gene pools of the groups, thus preventing the development of differences in genetic variation that would have led to full speciation.
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The range of the house sparrow has expanded dramatically due to human activities. Birds live and breed in most terrestrial habitats and on all seven continents, reaching their southern extreme in the snow petrel's breeding colonies up to inland in Antarctica. The highest bird diversity occurs in tropical regions. It was earlier thought that this high diversity was the result of higher speciation rates in the tropics; however recent studies found higher speciation rates in the high latitudes that were offset by greater extinction rates than in the tropics.
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A pair of Italian sparrows, in Rome The genus Passer contains about 25 species, depending on the authority, 26 according to the Handbook of the Birds of the World. Most Passer species are dull-coloured birds with short, square tails and stubby, conical beaks, between long. Mitochondrial DNA studies suggest that speciation in the genus occurred during the Pleistocene and earlier, while other evidence suggests speciation occurred 25,000 to 15,000 years ago. Within Passer, the house sparrow is part of the "Palaearctic black-bibbed sparrows" group and a close relative of the Mediterranean "willow sparrows".
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The presence of pollen competition when outcrossing occurs in a plant that utilizes self-fertilization allows recognition and selection of different pollen grains to fertilize the ovule. A. thaliana is closely related to Arabidopsis lyrata being that one diverged from the other through speciation. Although speciation has separated these species, they are still capable of providing a means of outcrossing between each other, initiating pollen competition within the plant. Although competition does occur among male gametophytes of both species, A. lyrata has very low instances of adaptive evolution compared to A. thaliana.
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William R. Rice and Ellen E. Hostert (1993) conclude that the observed prezygotic isolation in their studies is a product of pleiotropy's balancing role in indirect selection. By imitating the traits of all-infertile hybridized species, they noticed that the fertilization of eggs was prevented in all eight of their separate studies, a likely effect of pleiotropic genes on speciation. Likewise, pleiotropic gene's stabilizing selection allows for the allele frequency to be altered. Studies on fungal evolutionary genomics have shown pleiotropic traits that simultaneously affect adaptation and reproductive isolation, converting adaptations directly to speciation.
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Evolutionary biology is the study of the evolutionary processes that have shaped the diversity of life on Earth. It incorporates genetics, ecology, biogeography, and paleontology to analyze topics including natural selection, variance, adaptation, divergence, genetic drift, and speciation.
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Additionally she found that anti-Xh was reactive in the sera of Old and New world monkeys but not of Prosimian or lesser mammals, concluding that the isotypic specificity among the higher mammals arose during the speciation process.
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Polymorphism is one good way the opportunities get to be used; it has survival value, and the selection of modifier genes may reinforce the polymorphism. In addition, polymorphism seems to be associated with a higher rate of speciation.
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In two case studies in Cueva del Azufre and Cueva Luna Azufre in Tabasco, Mexico, the Atlantic molly is experiencing speciation. It is occurring between cave and surface populations as well as between habitats of varying sulfur concentrations.
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In 1978, Michael J. D. White wrote about an extension of the modern synthesis based on new research from speciation.Parnell, Dennis R. (1978). Heralding a New Synthesis Modes of Speciation by M. J. D. White. Systematic Botany. Vol.
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Concerns have been raised that the homogenizing of the environment may contribute to more and more fusion, leading to the loss of biodiversity. Seehausen, O. (2006). Conservation: losing biodiversity by reverse speciation. Current Biology, 16(9), R334-R337.
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Genetic evidence for the hybrid origin of the diploid plant Stephanomeria diegensis. Evolution 36:6 1158-67. Furthermore, it is thought to be the result of homoploid hybrid speciation, which is uncommon.Sherman, N. A. & J. M. Burke. (2009).
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The Taurus Mountains provide a cool damp climate for species that cannot survive the hot dry summer climate on either side, and this could have encouraged survival and speciation, resulting in the many endemic species found here today.
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New York: Columbia University Press. pp. 216–248. . it can be inferred that Alticonodon was hypercarnivorous. This ecological speciation might have come due to competition with other mammals in the region, such as the various metatherians.R. C. Fox. 1969.
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Drawing on more recent studies of molecular data, Ted R. Anderson stated in his 2006 Biology of the Ubiquitous House Sparrow that all Passer species have a long evolutionary history, with speciation possibly occurring as early as the Miocene.
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Speciation in flowering plants. Science 152: 167–172. It has been suggested (Carr, 1980, 2000) that the Calycadenia pauciflora could have originated directly from an ancestral race through a single saltational event involving multiple chromosome breaks.Carr, G. D. (1980).
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In Anatolia the Pleistocene glaciations only covered the highest peaks, so there are many species with small ranges. In other words: Anatolia as a whole is a big “massif de refuge”, showing all degrees of past and recent speciation.
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Blakiella is a monotypic genusVargas, O. M. and S. Madrinán. (2012). Preliminary phylogeny of Diplostephium (Asteraceae): Speciation rate and character evolution. Lundellia 15, 1-15. of flowering plants in the aster family, Asteraceae, containing the single species Blakiella bartsiifolia.
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Godfrey Matthew Hewitt (10 January 1940 – 18 February 2013) was a British professor and evolutionary geneticist at the University of East Anglia who was very influential in the development of the fields of molecular ecology, phylogeography, speciation and hybridisation.
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Gryllus pennsylvanicus is known as the fall field cricket. G. pennsylvanicus is common in southern Ontario, is widespread across much of North America Alexander, R. D. 1968. Life cycle origins, speciation, and related phenomena in crickets. Q. Rev. Biol.
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Pulmonaria is a genus in the Boraginoideae subfamily of Boraginaceae, consisting of approximately 18 species, although species delineation (speciation) has proved problematic. Within the Boraginoideae, Pulmonaria is placed in the tribe Boragineae, where it is closely related to Borago.
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Humid conditions caused migration of modern Asian mammals northward, dependent on the climatic belts. Uncertainty remains for the timing and tempo of migration. The increase in mammalian abundance is intriguing. Increased levels may have promoted dwarfing – which may have encouraged speciation.
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Some Haemulon species eat plankton in the open water, but most seek small prey on the seabed.Rocha, L. A., et al. (2008). Historical biogeography and speciation in the reef fish genus Haemulon (Teleostei: Haemulidae). Molecular Phylogenetics and Evolution 48 918-28.
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With a great capacity for adaptation, ivy will grow wherever development conditions and habitat similar to that of its European origins exist, occurring as opportunistic species across a wide distribution with close vicariant relatives and few species, indicating recent speciation.
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Heliconius heurippa is a butterfly of the genus Heliconius that is believed by some scientists to be a separate species from--but a hybrid of--the species Heliconius cydno and Heliconius melpomene, making H. heurippa an example of hybrid speciation.
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Haploid '1C' genome sizes in Brachionus species range at least from 0.056 to 0.416 pg.Stelzer, C.P., Riss, S., Stadler, P. (2011) Genome size evolution at the speciation level: The cryptic species complex Brachionus plicatilis (Rotifera) BMC Evolutionary Biology 11: 90.
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Invaders are identified and removed by the ant colony, inhibiting competition and fungal interbreeding. This active isolation of individual populations helps maintain the genetic purity of the fungal colony, and this mechanism may lead to sympatric speciation within a shared habitat.
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It covers a broad spectrum of topics: genetic parentage, reproductive modes, population structure, speciation, hybridization, introgression, phylogeography, systematics, and phylogenetics. He has conducted research on diverse animal taxa ranging from corals and sponges to representatives of all the major vertebrate groups.
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The fruit of several species is edible, most notably B. gasipaes, while others are used medicinally or for construction. The ancestors of the genus are believed to have entered South America during the late Cretaceous. Bactris shows high rates of speciation.
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PTCHD4 has three other genes in its family: PTCHD1, PTCHD2, and PTCHD3, as well as the Niemann-Pick disease type C protein. These paralogs are far less conserved than strict orthologs, which may suggest that they split long before speciation.
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Morphologically differentiation is most reliably made through pore density of the basidiocarps as H. irregulare has a lower density than H. occidentale with more oblong and larger pores. The discovery of first generation hybrids in Montana could further confuse the speciation.
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Yang, Y., Servedio, M. R., & Richards-Zawacki, C. L. (2019). Imprinting sets the stage for speciation. Nature, 574(7776), 99-102. The population that goes extinct may leave behind some of its genes in the surviving population if they hybridize.
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Peripatric speciation also occurs on continents, as isolation of small populations can occur through various geographic and dispersion events. Laboratory studies have been conducted where populations of Drosophila, for example, are separated from one another and evolve in reproductive isolation.
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Aleksandr Nikolaevich Promptov (also spelled as Promptoff) (27 June 1898, Sevastopol - 11 November 1948, Koltushi) was a Russian and Soviet geneticist and ornithologist who studied bird calls, made recordings and suggested the role of vocalization and behavior in isolation and speciation.
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Extrapolationism is a sound working theory, with most evolutionary patterns the result of microevolutionary change over vast geological time. Major animal lineages are the result of ordinary speciation processes, although possibility-expanding changes may result in some form of lineage-level selection. In contrast, Gould sees selection as usually acting on organisms in a local population, although in theory and practice, it can occur at many levels, with change at one level often affecting future options at other levels. Selection can occur at the group level, with some species lineages having characteristics which make extinction less likely, or speciation more likely.
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In 1992, N. G. Marchant and Allen Lowrie described a new subspecies, D. gigantea subsp. geniculata, that grows to tall in black sandy soils near Perth and to its south. Jan Schlauer disagreed with Marchant and Lowrie's decision to give the new taxon a rank of subspecies and thus published a new combination of the taxon at the rank of variety in a 1996 issue of the Carnivorous Plant Newsletter. He argued that subspecies should be reserved for those occasions where allopatric, or geographically isolated, speciation occurred and varieties are best used in cases where sympatric speciation is suspected.
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Medium beaks had difficulty retrieving small seeds and were also not tough enough for the bigger seeds, and were hence maladaptive. While it is true that disruptive selection can lead to speciation, this is not as quick or straightforward of a process as other types of speciation or evolutionary change. This introduces the topic of gradualism, which is a slow but continuous accumulation of changes over long periods of time. This is largely because the results of disruptive selection are less stable than the results of directional selection (directional selection favors individuals at only one end of the spectrum).
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The second is a shift from an organism's ancestral ecology to a derived ecology, or a more true form of ecological fitting: traits are exapted from their original purpose to increase fitness. Finally, a more dramatic form involves the creation of new evolutionary arenas, requiring morphological or ecological changes to gain fitness under new conditions. Any of these processes can promote speciation or diversification under the right circumstances. Each form of ecological fitting can encourage speciation only if the population is sufficiently isolated from other populations to prevent gene flow from swamping local adaptation to newly formed species associations.
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Darwin's finches are a clear and famous example of divergent evolution, in which an ancestral species radiates into a number of descendant species with both similar and different traits. Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to speciation. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in allopatric or peripatric speciation) and experience different selective pressures that drive adaptations to their new environment. After many generations and continual evolution, the populations become less able to interbreed with one another.
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Electrospray ionization mass spectrometry is a very versatile technique, consisting in a transfer of the formed complexes from the injected solution to the gas phase by a soft ionization process without strongly perturbing the complex stability. In addition, a small amount of the prepared solution needs to be injected to obtain the speciation spectra. Speciation of several metal ions can be investigated in monophasic solutions at increasing ligand concentration in order to explore all potential complexes. Collision Induced Dissociation (CID) analysis can be also performed to assess the kinetic stability of the formed complexes by discovering the main fragmentation pathway of the ligand.
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For some time it was difficult to prove that sympatric speciation was possible, because it was impossible to observe it happening. It was believed by many, and championed by Ernst Mayr, that the theory of evolution by natural selection could not explain how two species could emerge from one if the subspecies were able to interbreed. Since Mayr's heyday in the 1940s and 50s, mechanisms have been proposed that explain how speciation might occur in the face of interbreeding, also known as gene flow. And even more recently concrete examples of sympatric divergence have been empirically studied.
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A species complex typically forms a monophyletic group that has diversified rather recently, as is shown by the short branches between the species A–E (blue box) in this phylogenetic tree. Species forming a complex have typically diverged very recently from each other, which sometimes allows the retracing of the process of speciation. Species with differentiated populations, such as ring species, are sometimes seen as an example of early, ongoing speciation: a species complex in formation. Nevertheless, similar but distinct species have sometimes been isolated for a long time without evolving differences, a phenomenon known as "morphological stasis".
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Seemingly, all these cases illustrate the manner in which speciation mechanisms originated in nature, therefore they are collectively known as "speciation genes", or possibly, gene sequences with a normal function within the populations of a species that diverge rapidly in response to positive selection thereby forming reproductive isolation barriers with other species. In general, all these genes have functions in the transcriptional regulation of other genes. The Nup96 gene is another example of the evolution of the genes implicated in post-copulatory isolation. It regulates the production of one of the approximately 30 proteins required to form a nuclear pore.
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Trisecphora is one of three daughter genera of the Oligocene to Miocene ecphora Ecphorosycon, the other two being Siphoecphora, and Chesathais. Trisecphora and its sister genera diverged from Ecphorosycon during a speciation event during the Aquitanian epoch in the Chesapeake Bay. During the Langhian epoch, Trisecphora underwent its own speciation event where several species, and the first of a divergent lineage, Ecphora wardi of genus Ecphora, were produced. Species of Trisecphora coexisted with Ecphorosycon, Chesathais, and Ecphora (together with its subgenus Planecphora), until the beginning of the Serravallian, when Ecphorosycon went extinct (Trisecphora's sister genus, Siphoecphora would later go extinct during the Langhian).
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It argues that the formation and movement of the Amazon and some of its tributaries presented a significant enough barrier to movement for wildlife populations to precipitate allopatric speciation. Facing different selection pressures and genetic drift, the divided populations diverged into separate species. There are several observable qualities that should be present if speciation has resulted from a river barrier. Divergence of species on either side of the river should increase with the size of the river, expressing weakly or not at all in the headwaters and more strongly in the wider, deeper channels further downriver.
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The patterns of speciation in the family Lauraceae, where Misanteca genus belong, indicate that since the onset of aridification on the continents 15 million years ago, rainforest diversified in species numbers with the majority of species the product of vicariance. One of the products of aridification is the current island like archipelagos of rainforests along the planet. The fragmentation of once more continuous rainforest facilitated isolation of populations and this likely caused the increase in the rate of speciation as found in the Lauraceae. Many botanical species are having similar foliage to the Lauraceae due to convergent evolution.
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Hollies (here, Ilex aquifolium) are dioecious: (above) shoot with flowers from male plant; (top right) male flower enlarged from female plant; (lower right) female flower enlarged, showing stamen and reduced, sterile stamens with no pollen. The phylogeography of this group provides examples of various speciation mechanisms at work. In this scenario ancestors of this group became isolated from the remaining Ilex when the Earth mass broke away into Gondwana and Laurasia about 82million years ago, resulting in a physical separation of the groups and beginning a process of change to adapt to new conditions. This mechanism is called allopatric speciation.
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This conclusion was rejected as unwarranted by Wakeley (2008), who suggested alternative explanations, including selection pressure on the X chromosome in the populations ancestral to the CHLCA. Complex speciation and incomplete lineage sorting of genetic sequences seem to also have happened in the split between the human lineage and that of the gorilla, indicating "messy" speciation is the rule rather than the exception in large primates. Such a scenario would explain why the divergence age between the Homo and Pan has varied with the chosen method and why a single point has so far been hard to track down.
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However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered a rare event. However, hybridization resulting in reproductive isolation is considered an important means of speciation in plants, since polyploidy (having more than two copies of each chromosome) is tolerated in plants more readily than in animals. Polyploidy is important in hybrids as it allows reproduction, with the two different sets of chromosomes each being able to pair with an identical partner during meiosis. Polyploids also have more genetic diversity, which allows them to avoid inbreeding depression in small populations.
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Therefore, the Gottlieb and Ford concluded that these two species were related as progenitor and derivative. Gottlieb proposed that L. discoidea arose relatively recently from adaptation to serpentine soils, also as an example of quantum speciation. In his 2003 review, Gottlieb summarized: > The general lesson from the review of these studies is that quantum > speciation remains an important and useful concept that can be applied to a > greater variety of situations than initially envisaged. The genetic and > chromosomal changes need not be as radical as once supposed, and a new > species may originate and persist even without novel adaptations.
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Haldane himself described the rule as: Haldane's rule applies to the vast majority of heterogametic organisms. This includes the case where two species make secondary contact in an area of sympatry and form hybrids after allopatric speciation has occurred. The rule includes both male heterogametic (XY or XO-type sex determination, such as found in mammals and Drosophila fruit flies) and female heterogametic (ZW-type sex determination, as found in birds and butterflies), and some dioecious plants such as campions. Hybrid dysfunction (sterility and inviability) is a major form of post-zygotic reproductive isolation, which occurs in early stages of speciation.
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Albania's section of Great Prespa is recognised as a wetland of international importance by designation under the Ramsar Convention and further as an Important Bird and Plant Area. Both lakes are essentially situated between 850 and 900 metres elevation above the Adriatic. Located about 150 metres above Lake Ohrid, their waters passes through several karst underground channels emerging from springs into the lake.Thomas Wilke, Risto Väinolä, Frank Riedel (2009), Patterns and Processes of Speciation in Ancient Lakes: Proceedings of the Fourth Symposium on Speciation in Ancient Lakes, Berlin, Germany, September 4-8, 2006 (Developments in Hydrobiology), p.
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A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. Hybrid zones can form in situ due to the evolution of a new lineage but generally they result from secondary contact of the parental forms after a period of geographic isolation, which allowed their differentiation (or speciation). Hybrid zones are useful in studying the genetics of speciation as they can provide natural examples of differentiation and (sometimes) gene flow between populations that are at some point between representing a single species and representing multiple species in reproductive isolation.
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Joint Expert Speciation System (JESS) is a package of computer software and data developed collaboratively at Murdoch University and elsewhere by researchers interested in the chemical thermodynamics of water solutions with important applications in industry, biochemistry, medicine and the environment. Using information from the chemical literature, stored in databases for numerous chemical properties, JESS achieves coherence between frequently conflicting sources by automatic methods. JESS places a strong emphasis on the concept of chemical speciation (i.e. the identity and relative abundance of different chemical entities which may be present), which can be predicted from known stability constants of metal-ligand complexes.
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De Queiroz also has interests in theoretical and conceptual topics in systematic and evolutionary biology. He published an article early in his career on the relationship between the sequence of ontogenetic transformations and phylogenetic inference. Beginning in 1998, he published a series of articles proposing how to achieve a unified species concept and outlining several of its consequences.de Queiroz, K. (1998) “The general lineage concept of species, species criteria, and the process of speciation: A conceptual unification and terminological recommendations.” Pp. 57–75 (Chapter 5) in “Endless Forms: Species and Speciation,” D. J. Howard and S. H. Berlocher (eds.).
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In one population, one of the two equivalent locci (A) is expressed while the other (B) has been silenced, while in the other population the reciprocal pattern occurs, with B being expressed and A silenced. It is important to note that this refers to equivalent loci, specific locations within the genome, rather than the entire homeologous chromosome. Reciprocal silencing on the population level has been proposed as a means of allopatric speciation following a polyploid event. Allopatric speciation occurs when two populations of the same species become spatially separated and accumulate enough genetic differences to lose the ability to interbreed.
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First, two former subspecies of N. menagensis were elevated to the two distinct species N. bancanus and N. borneanus. Further, N. kayan was recognized as a new species that is also distinct from the nominate subspecies, N. menagensis. All newly recognized or elevated species showed significant differences in their "facemask"—the coloration patterns on their face. Analysis of the facemask patterns suggests that N. kayan diverged from N. menagensis and N. borneanus through sympatric speciation (divergent evolution of organisms living in the same geographic region), while geographic barriers may account for its divergence with N. bancanus (allopatric speciation).
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Consequently, "An increase of genotypes adapted to the xeric aspects of a given site would be expected as a result of prolonged drought..." In 1959 Lewis and Epling reported on a rapid speciation event at the diploid level by hybridization. They asserted that D. gypsophilum arose from the hybridization of D. recurvatum and D. hesperium in a single generation; and presented evidence that D. gypsophilum was not only intermediate in morphology, but occupied an ecological zone intermediate between the two parents. Further, all the species were interfertile. They also concluded that this mode of speciation was not unique in Delphinium.
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Due to the dispersal capabilities of albatross, distance between populations does not appear to be a determining factor in divergence. Actual speciation is likely to occur very slowly, as the selective pressures on the animals are the same for the vast majority of their lives, which is spent at sea. Small mutational changes in non-nuclear DNA that become fixed in small populations are likely to be the major driver of speciation. That there is minimal structural morphological difference between the genetically distinct populations is evidence for random genetic drift, rather than directional evolution due to natural selective pressure.
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Doebeli and Dieckmann developed a mathematical model that suggested that ecological contact is an important factor in parapatric speciation and that, despite gene flow acting as a barrier to divergence in the local population, disruptive selection drives assortative mating; eventually leading to a complete reduction in gene flow. This model resembles reinforcement with the exception that there is never a secondary contact event. The authors conclude that, "spatially localized interactions along environmental gradients can facilitate speciation through frequency-dependent selection and result in patterns of geographical segregation between the emerging species." However, one study by Polechová and Barton disputes these conclusions.
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Containing less genetic variation from the main population, shifts in allele frequencies may occur from different selection pressures. This to further changes in the network of linked loci, driving a cascade of genetic change, or a "genetic revolution"—a large-scale reorganization of the entire genome of the peripheral population. Mayr did recognize that the chances of success were incredibly low and that extinction was likely; though noting that some examples of successful founder populations existed at the time. Shortly after Mayr, William Louis Brown, Jr. proposed an alternative model of peripatric speciation in 1957 called centrifugal speciation.
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The pronophilines have been involved in diverse biogeographical discussions that aim to explain their current distribution, diversity and endemism.A.L. Viloria 2003 "Historical biogeography and the origins of the satyrine butterflies of the tropical Andes (Lepidoptera: Rhopalocera)", In: Llorente J. Morrone, J.J. (Eds.) Una perspectiva latinoamericana de la biogeografía Universidad Autónoma de México, México. The high diversity within the Pronophilina, and the distinctive speciation patterns in mountain and Caribbean taxa, has also motivated discussion about parapatric and sympatric speciation.Michael J Adams 1985 Speciation in the pronophiline butterflies () of the northern {Andes} Journal of Research on the Lepidoptera Supl.
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Basic heteroaromatic boronic acids (boronic acids that contain a basic nitrogen atom, such as 2-pyridine boronic acid) display additional protodeboronation mechanisms. A key finding shows the speciation of basic heteroaromatic boronic acids to be analogous to that of simple amino acids, with zwitterionic species forming under neutral pH conditions. For the 2-pyridine boronic acid, the zwitterionic compound is responsible for its rapid protodeboronation under neutral pH, through a unimolecular fragmentation of the C-B bond. In fact, the addition of acid (H+) or hydroxide (OH-) acts to attenuate protodeboronation by shifting the speciation away from the reactive zwitterion.
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The "rock-paper- scissors" mating strategy is a genetically-based male polymorphism that has been maintained over millions of years throughout many populations of side- blotched lizard in the United States and Mexico. However, speciation has resulted from the formation of reproductive isolation between populations when a population loses of one or more of the male morphologies. However, speciation due to the loss of a male morph has occurred when populations lose one or more male morphs and become reproductively isolated from populations with the ancestral polymorphism. For side-blotched lizards, the morph lost most commonly is the sneaker male.
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However, at the southern edge of the Central Valley, where the Sierra foothill populations come into contact with those of the Coast Range, the populations do not interbreed, instead acting as distinct species. This phenomenon is known as a ring speciation, with different populations representing different stages of speciation, the process by which one species becomes two. Zoologist Arnold Grobman called Stebbins' research "without doubt, the most outstanding study of a genus of American salamanders that has yet appeared." The Ensatina complex has been the focus of research ever since, and is a widely used textbook example of evolutionary processes.
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Louis Euzet created the concept of alloxenic speciation, i.e. the speciation of parasites linked with the behaviour and ecology of the host, and was one of the first to propose schemes of coevolution between monogeneans and elasmobranchs. His laboratory in Montpellier was a hub where many students and researchers visited, and his small laboratory in the Station de Biologie Marine at Sète was still much frequented 10 years after his official retirement. Most of Louis Euzet's scientific work was devoted to the Mediterranean, but he also worked on parasites from almost all of the world's seas.
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Paralogous genes are genes that are related via duplication events in the last common ancestor (LCA) of the species being compared. They result from the mutation of duplicated genes during separate speciation events. When descendants from the LCA share mutated homologs of the original duplicated genes then those genes are considered paralogs. As an example, in the LCA, one gene (gene A) may get duplicated to make a separate similar gene (gene B), those two genes will continue to get passed to subsequent generations. During speciation, one environment will favor a mutation in gene A (gene A1), producing a new species with genes A1 and B. Then in a separate speciation event, one environment will favor a mutation in gene B (gene B1) giving rise to a new species with genes A and B1. The descendants’ genes A1 and B1 are paralogous to each other because they are homologs that are related via a duplication event in the last common ancestor of the two species.
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Although Darwin himself observed that inbred features of fancy pigeons were inherited in accordance with Mendel's laws (although Darwin didn't actually know about Mendel's ideas when he made the observation), it was not obvious that these features selected by fancy pigeon breeders can similarly explain quantitative variation in nature. An early attempt by William Ernest Castle to unify the laws of Mendelian inheritance with Darwin's theory of speciation invoked the idea that species become distinct from one another as one species or the other acquires a novel Mendelian factor. Castle's conclusion was based on the observation that novel traits that could be studied in the lab and that show Mendelian inheritance patterns reflect a large deviation from the wild type, and Castle believed that acquisition of such features is the basis of "discontinuous variation" that characterizes speciation. Darwin discussed the inheritance of similar mutant features but did not invoke them as a requirement of speciation.
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In 1962 Lewis published a more lengthy proposal for "catastrophic selection" as the primary mode of speciation in Clarkia: > ...catastrophic selection in ecologically marginal populations has had a > prominent role in speciation in the genus Clarkia.The following observations > compellingly suggest that speciation at the diploid level in this genus > ordinarily involves a rapid reorganization of the genome associated with > ecological differentiation, a reorganization that involves an intermediate > stage of low fertility: Closely related pairs of species bear a relationship > of parent to offspring and not one of siblings. They invariably differ by > several gross structural rearrangements of the chromosomes, and sometimes by > a change in basic number; as a consequence, hybrids between them are > essentially sterile. Recent derivatives occur at the margin of distribution > of the parental species,but the two species are unable to form stable mixed > populations because sterile hybrids are formed as readily as intraspecific > progenies; the derivative populations must, therefore, have arisen in > isolation.
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Also, the pink-flowered selfer is inter-fertile with outcrossing populations, while the white flowered self-pollinated population differs from the others by a translocation and reduced fertility. He argued that the self- pollinated populations arose from catastrophic selection; the self-pollinators being able to survive extremely reduced population sizes; they concluded that the white flowered population was a derivative of the pink flowered selfing population. In 1966 Lewis expanded the concept of catastrophic selection to "saltational speciation" to all flowering plants: > Saltational speciation in flowering plants is required as an explanation > only for the relationships between particular populations of annuals that > have been studied intensively. by reasonable extrapolation, however, it > appears to be the prevalent mode of speciation in many herbaceous genera and > to have had a significant role in the evolution of woody plants In 1968 Wedberg and Lewis reported on the distribution of widespread translocation heterozygosity and supernumerary chromosomes in C. williamsonii.
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Quasillites is a fossil genus of ostracod from the Devonian and Carboniferous Periods.J. J. Sepkoski Jr. 1998. Rates of speciation in the fossil record. Philosophical Transactions of the Royal Society Biological Sciences 353(1366):315-326Moore, R., Lalicker, C., Fischer, A. 1952.
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Mitochondrial DNA invariability also suggests recent radiation of these clades, probably within the last 200,000 years. These findings are consistent with the Pleistocene refugia hypothesis: in the late Pleistocene epoch, climate change reduced once widespread habitable forest areas, resulting in allopatric speciation.
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Florin, Ann-Britt. "Bottlenecks and Blowflies: Speciation, Reproduction and Morphological Variation in Lucilia." Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology (2001): 660-700. Upon hatching, Lucilia illustris enters its larval stages of development, commonly called a maggot.
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Nepenthes di Sumatera: The genus Nepenthes of the Sumatra Island. In: M. Hotta (ed.) Diversity and Dynamics of Plant Life in Sumatra: Forest Ecosystem and Speciation in Wet Tropical Environments. Part 1: Reports and Collection of Papers. Kyoto University, Kyoto. pp. 75–109.
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Tamin, R. & M. Hotta 1986. Nepenthes di Sumatera: The genus Nepenthes of the Sumatra Island. In: M. Hotta (ed.) Diversity and Dynamics of Plant Life in Sumatra: Forest Ecosystem and Speciation in Wet Tropical Environments. Part 1: Reports and Collection of Papers.
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Several species of Eubranchus were transferred to Amphorina in 2020.Korshunova, T.; Malmberg, K.; Prkić, J.; Petani, A.; Fletcher, K.; Lundin, K.; Martynov, A. (2020). Fine-scale species delimitation: speciation in process and periodic patterns in nudibranch diversity. ZooKeys. 917: 15-50.
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In the past, this likely contributed to speciation. H. pachinus is also known to hybridize with H. melpomene. The fact that both species hybridize with H. melpomene is considered significant because H. melpomene exhibits a distinct pheromonal chemistry and coloring.Schulz, Stefan, et al.
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Several species of Eubranchus were transferred to Amphorina in 2020.Korshunova, T.; Malmberg, K.; Prkić, J.; Petani, A.; Fletcher, K.; Lundin, K.; Martynov, A. (2020). Fine-scale species delimitation: speciation in process and periodic patterns in nudibranch diversity. ZooKeys. 917: 15-50.
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Several species of Eubranchus were transferred to Amphorina in 2020.Korshunova, T.; Malmberg, K.; Prkić, J.; Petani, A.; Fletcher, K.; Lundin, K.; Martynov, A. (2020). Fine-scale species delimitation: speciation in process and periodic patterns in nudibranch diversity. ZooKeys. 917: 15-50.
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The two populations may fuse back into one population. This tends to occur when there is little to no reproductive isolation between the two. During the process of fusion a hybrid zone may occur. This is sometimes called introgressive hybridization or reverse speciation.
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29th meeting of the Standing Committee, Bern.Yesson, C., Toomey, N. H. and Culham, A. (2009) Cyclamen: time, sea and speciation biogeography using a temporally calibrated phylogeny. Journal of Biogeography, 36 (7). pp. 1234–1252. ISSN 0305-0270 doi: 10.1111/j.1365-2699.2008.01971.
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At this time, the area was covered by a sea, which created a geographic barrier which caused this ancestral species to diverge from S. oedipus through the process of allopatric speciation. Today, the two species are principally separated by the Atrato river.
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Rocha has authored one book and more than 100 scientific articles. He is best known for his work in speciation in coral reef fishes using advanced genomic methodologies, and recently has been actively exploring the diversity of deep coral reefs throughout the tropics.
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"Mercury speciation in drainage from the New Idria mercury mine, California." Environmental science & technology 34.22 (2000): 4773-4779 Gustin, Mae Sexauer, et al. "Assessing the contribution of natural sources to regional atmospheric mercury budgets." Science of the Total Environment259.1 (2000): 61-71.
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These hybrid zones are useful as biological model systems for studying the mechanisms of speciation. Recently DNA analysis of a bear shot by a hunter in the North West Territories confirmed the existence of naturally-occurring and fertile grizzly–polar bear hybrids.
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The mode of evolution of sex pheromones in Bactrocera has occurred by rapid saltational changes associated with speciation followed by gradual divergence thereafter.Symonds, Matthew R. E., Moussalli, Adnan and Elgar, Mark A. (2009). The evolution of sex pheromones in an ecologically diverse genus of flies.
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The speciation of M. scandinavica was determined by 16S rRNA gene sequencing. Protein and physiological analysis of the cells were also undertaken. The DNA- DNA hybridization technique comparing the isolated Methylomonas species in vitro with other Type I methanotrophs; values did not exceed 65%.
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Terraces, tilting, and topography of Cordell Bank, California. California Geology 40(11):258–264. morphology and speciation of a resident gastropod,Schmieder, R. W. 1980. Intermediate forms and range extension of Pedicularia californica and Pedicularia ovuliformis, Veliger, 22(4):382–384.Schmieder, R. W. 1982.
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Erythranthe peregrina is a species of monkeyflower. Its Latin name means "foreign", or more loosely "the foreigner". This species is a rare example of polyploidization and speciation where sterility did not occur. It was discovered in 2011, first reported in 2012, and named Mimulus peregrinus.
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Major speciation events of radiolarians occurred during the Mesozoic. Many of those species are now extinct in the modern ocean. Scientists hypothesize that competition with diatoms for dissolved silica during the Cenozoic is the likely cause for the mass extinction of most radiolarian species.
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Drosophila sechellia is a species of fruit fly, used in lab studies of speciation because it can mate with Drosophila simulans. Drosophila sechellia is endemic to (some of) the Seychelles, and was one of 12 fruit fly genomes sequenced for a large comparative study.
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Jürgen Haffer (9 December 1932 in Berlin – 26 April 2010 in Essen) was a German ornithologist, biogeographer, and geologist. He is most remembered for his theory of Amazonian forest refugia during the Pleistocene that would have contributed to speciation and the diversification of the biota.
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Secale vavilovii is the most different of the genus as it separated early from the other species in the genus.Cuadrado, A., & Jouve, N. (2002). Evolutionary trends of different repetitive DNA sequences during speciation in the genus Secale. The Journal of Heredity, 93(5), 339–345.
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A few other Poecilia species are known from similar habitats in Mexico.Palacios, Arias- Rodriguez, Plath, Eifert, Lerp, Lamboj, Voelker, & Tobler (2013). The Rediscovery of a Long Described Species Reveals Additional Complexity in Speciation Patterns of Poeciliid Fishes in Sulfide Springs. PLoS ONE 8(8): e71069.
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Tyrannosaurus rex. Non-avian dinosaurs died out in the Cretaceous–Paleogene extinction event at the end of the Cretaceous period. Extinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction.
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Selection against the heterozygote would then directly create reproductive isolation, leading to the Bateson–Dobzhansky–Muller model, further elaborated by H. Allen Orr and Sergey Gavrilets. With reinforcement, however, natural selection can favor an increase in pre-zygotic isolation, influencing the process of speciation directly.
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Antarctic and common minke whales diverged from each other in the Southern Hemisphere 4.7 million years ago, during a prolonged period of global warming in the early Pliocene which disrupted the Antarctic Circumpolar Current and created local pockets of upwelling, facilitating speciation by fragmenting populations.
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Species of Phytophthora have been shown to have evolved by the interspecific hybridization of two different species from the genus.Brasier, C. and E.M. Hansen, Evolutionary Biology of Phytophthora PART II: Phylogeny, Speciation, and Population Structure. Annual Review of Phytopathology, 1992. 30: p. 173-200.
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The Clymene dolphin (Stenella clymene), in older texts known as the short- snouted spinner dolphin, is a dolphin endemic to the Atlantic Ocean. It is the only confirmed case of hybrid speciation in marine mammals, descending from the spinner dolphin and the striped dolphin.
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91, pp. 133-144. The following pluvial (rain) periods allowed the whipbirds on the western side to migrate east and take up areas near the Murray basin.Cracraft, J., 1986. Origin and evolution of continental biotas: speciation and historical congruence within the Australian avifauna. Evolution. Vol.
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Evolutionary Dynamics of a Natural Population: The Large Cactus Finch of the Galápagos, p. 241. Chicago: Chicago U. Pr. In 1999 Peter Grant agreed that "sympatric speciation [in this example] is unlikely to occur".Grant, Peter R. 1999. Ecology and Evolution of Darwin's Finches.
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The existence of a separate species was first hinted at by the discovery of two distinct breeding seasons of Oceanodroma storm-petrels in the Azores.Monteiro, L.R. & Furness, R.W. (1998). "Speciation through temporal segregation of Band-rumped Storm Petrel (Oceanodroma castro) populations in Azores?" Phil. Trans.
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The rainbow trout has been reported to hybridize with at least two other salmonid species. Additionally, the cichlids in Lake Victoria evolved over 700 unique species in only 150,000 years and are theorized to have done so via ancient hybridization events which led to speciation.
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Hybrid fruits are created through the controlled speciation of fruits that creates new varieties and cross-breeds. Hybrids are grown using plant propagation to create new cultivars. This may introduce an entirely new type of fruit or improve the properties of an existing fruit.
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The species' scientific and common names are derived from the Bugun tribe in whose communal forests the species was discovered. The species is a sister of Liocichla omeiensis and the speciation may have been caused by the isolating geographic barrier of the Hengduan mountains.
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Richards pointed out > [Richard A. Richards, The Species Problem: A Philosophical Analysis, > Cambridge University Press, 2010] that Linnaeus saw species as eternally > fixed in his very first publication from 1735, but only a few years later he > discovered hybridization as a modus for speciation.
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He was the first to encapsulate the then contemporary literature in his 1942 publication Systematics and the Origin of Species, from the Viewpoint of a Zoologist and in his subsequent 1963 publication Animal Species and Evolution. Like Jordan's works, they relied on direct observations of nature, documenting the occurrence of geographic speciation. He described the three modes: geographic, semi-geographic, and non-geographic; which today, are referred to as allopatric, parapatric, and sympatric respectively. Mayr's 1942 publication, influenced heavily by the ideas of Karl Jordan and Poulton, was regarded as the authoritative review of speciation for over 20 years—and is still valuable today.
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Therefore, butterflies will tend to mate with others of the same wing pattern promoting increased fitness, eventually eliminating the heterozygote altogether. This unfavorable heterozygote generates pressure for a mechanism that cause assortative mating which will then lead to reproductive isolation due to the production of post-mating barriers. It is actually fairly common to see sympatric speciation when disruptive selection is supporting two morphs, specifically when the phenotypic trait affects fitness rather than mate choice. In both situations, one where intraspecific competition is at work and the other where it is not, if all these factors are in place, they will lead to reproductive isolation, which can lead to sympatric speciation.
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It is more useful to think of a continuum, on which there are limitless levels of geographic and reproductive overlap between species. On one extreme is allopatry, in which the overlap is zero (no gene flow), and on the other extreme is sympatry, in which the ranges overlap completely (maximal gene flow). The varying definitions of sympatric speciation fall generally into two categories: definitions based on biogeography, or on population genetics. As a strictly geographical concept, sympatric speciation is defined as one species diverging into two while the ranges of both nascent species overlap entirely – this definition is not specific enough about the original population to be useful in modeling.
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Saxifraga osloensis, a natural tetraploid hybrid species Since plants are more tolerant of polyploidy, hybrid species are more common than in animals. Estimates indicate as many as 2–4% of all flowering plants and 7% of all fern species are the results of polyploid hybridization. Many crop species such as wheat are hybrids, and hybridization is an important factor in speciation in some plant groups. Garden flowers in the genus Saxifraga are often hybrids, and a tetraploid natural hybrid, Saxifraga osloenis, is thought to have formed at the end of the last ice age.. Homoploid speciation also occurs in plants, and has for example given rise to several species of sunflower.
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Model of the speciation of Hominini and Gorillini over the past 10 million years; the hybridization process within Hominini is indicated as ongoing during roughly 8 to 6 Mya. The chimpanzee–human last common ancestor (CHLCA) is the last common ancestor shared by the extant Homo (human) and Pan (chimpanzee and bonobo) genera of Hominini. Due to complex hybrid speciation, it is not possible to give a precise estimate on the age of this ancestral population. While "original divergence" between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recently as 4 million years ago (Pliocene).
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Following behind Wright, Ernst Mayr created many persuasive models to show that the decline in genetic variation and small population size accompanying the founder effect were critically important for new species to develop. However, much less support for this view is shown today, since the hypothesis has been tested repeatedly through experimental research, and the results have been equivocal at best. Speciation by genetic drift is a specific case of peripatric speciation which in itself occurs in rare instances. It takes place when a random change in genetic frequency of population favours the survival of a few organisms of the species with rare genes which cause reproductive mutation.
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In Otte, D. and Endler, John A. (eds) Speciation and its Consequences, Sinauer Associates, pp. 158–179, A similar pattern exists with Allonemobius fasciatus and A. socius, species of ground crickets in eastern North America. Males in sympatric populations of the damselflies Calopteryx maculata and C. aequabilis are able to discriminate between females of different species better than those in allopatric populations; with females of C. aequabilis in sympatric populations exhibiting lighter wing colors compared to allopatric females—an illustration of reproductive character displacement. Fifteen species of sympatrically distributed Agrodiaetus butterflies with pronounced differences in wing color pattern likely arose as a result of speciation by reinforcement.
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Coyne and Orr surveyed 171 species pairs, collecting data on their geographic mode, genetic distance, and strength of both prezygotic and postzygotic isolation; finding that prezygotic isolation was significantly stronger in sympatric pairs, correlating with the ages of the species. Additionally, the strength of post-zygotic isolation was not different between sympatric and allopatric pairs. This finding supports the predictions of speciation by reinforcement and correlates well with a later study that found 33 studies expressing patterns of strong prezygotic isolation in sympatry. A survey of the rates of speciation in fish and their associated hybrid zones found similar patterns in sympatry, supporting the occurrence of reinforcement.
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The other island Mal Grad ("Small Town", in Albania) is the site of a ruined 14th century monastery dedicated to St. Peter. Today, both islands are uninhabited. Because Great Prespa Lake sits in limestone country about 150m above Lake Ohrid, which lies only about (6 miles) to the west, the only outlets for its waters are through underground channels in the karst and emerge from springs which feed streams running into Lake Ohrid.Thomas Wilke, Risto Väinolä, Frank Riedel (2009), Patterns and Processes of Speciation in Ancient Lakes: Proceedings of the Fourth Symposium on Speciation in Ancient Lakes, Berlin, Germany, September 4–8, 2006 (Developments in Hydrobiology), p.
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With this interpretation, his verbal, theoretical model can effectively produce a new species; of which was subsequently confirmed mathematically. Further mathematical models have been developed to demonstrate the possibility of clinal speciation with most relying on, what Coyne and Orr assert are, "assumptions that are either restrictive or biologically unrealistic". A mathematical model for clinal speciation was developed by Caisse and Antonovics that found evidence that, "both genetic divergence and reproductive isolation may therefore occur between populations connected by gene flow". This research supports clinal isolation comparable to a ring species (discussed below), except that the terminal geographic ends do not meet to form a ring.
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These adaptations, variations on habit, trunks, branches, branchlets, spines, leaves, or flowers, are plentiful in demonstrating how Pachypodium as a genus fosters greater variation in its speciation. The manner in which speciation occurs in Pachypodium, therefore, is apparent: adaptive mechanisms on a morphological level respond to the microenvironment of Pachypodium habitat. The genus' unique organizational, architectural morphology shapes plants that are highly, adaptively responsive to their immediate, surrounding, microenvironments. The duplicity of an adaptive mechanism that is at once "strict" and "flexible" at differing levels of plant physiology, or structure, has granted Pachypodium the ability to evolve within the landscape into variations that fulfill an ecological niche as various species.
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Around the same time, the botanist Verne Grant developed a model of quantum speciation very similar to Mayr's model in the context of plants. In what has been called Mayr's genetic revolutions, he postulated that genetic drift played the primary role that resulted in this pattern. Seeing that a species cohesion is maintained by conservative forces such as epistasis and the slow pace of the spread of favorable alleles in a large population (based heavily on J. B. S. Haldane's calculations), he reasoned that speciation could only take place in which a population bottleneck occurred. A small, isolated, founder population could be established on an island for example.
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Sexual selection pressures may become weakened by this in an isolated peripheral population, and as a by- product of the altered mating recognition system, secondary sexual traits may appear. Eventually, a growth in population size paired with novel female mate preferences will give rise to reproductive isolation from the main population- thereby completing the peripatric speciation process. Support for this model comes from experiments and observation of species that exhibit asymmetric mating patterns such as the Hawaiian Drosophila species or the Hawaiian cricket Laupala. However, this model has not been entirely supported by experiments, and therefore, it may not represent a plausible process of peripatric speciation that takes place in nature.
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Roger Butlin demarcated incomplete post-zygotic isolation from complete isolation, referring to incomplete isolation as reinforcement and completely isolated populations as experiencing reproductive character displacement.Butlin, Roger K. (1989). Reinforcement of premating isolation. In Otte, D. and Endler, John A. (eds) Speciation and its Consequences, Sinauer Associates, pp.
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The taxonomy of the genus is complex. A number of different schemes have been used, and up to 1,000 species have been identified at times, with approaches varying between wide and narrow concepts of speciation ('lumpers' and 'splitters'). Phylogenetic studies indicate seven major clades within the genus.
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Neodiprion abietis, a Diprinoid phytophagous specialist commonly known as the balsam fir sawfly is an insect found within Canada and throughout the United States.G. Knerer, C.E. Atwood (1973). Diprionid sawflies: polymorphism and speciation. Changes in diapause and choice of food plants led to new evolutionary units.
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Although regional variation in calling song and life history were noted,Rehn, J.A.G., and Hebard, M. (1915). The genus Gryllus (Orthoptera) as found in America. Proc. Acad. Nat. Sci. Phila. 67:292-322.Fulton, B. B. 1952. Speciation in the field cricket. Evolution 6, 283-295.
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These are both difficult requirements. Research projects can last longer than a researcher's career; for instance, research into mimicry started 150 years ago, and is still going strongly.Mallet J. and Joron M. 1999. Evolution in diversity in warning color and mimicry: polymorphisms, shifting balance and speciation.
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The sori are round, with a peltate indusium. The stipes have prominent scales. Hybridization and polyploidy are well-known phenomena in this group, with many species formed via these processes. The North American Dryopteris hybrid complex is a well-known example of speciation via allopolyploid hybridization.
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Quinaria species are related to the Drosophila cardini, Drosophila bizonata, and Drosophila testacea species groups. Evolutionary studies in these various mushroom-feeding Drosophila have contributed to understanding how symbiotic bacteria can drastically affect host evolution, the impact of various genetic elements in natural populations, and speciation.
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Genetic research has shown that their closed living relative is the bay-breasted warbler, the latter species perhaps specialized to forage in the same coniferous trees at lower levels.Lovette, I. J. and E. Bermingham. 1999. Explosive speciation in the New World Dendroica warblers. Proc. R. Soc.
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Haploid '1C' genome sizes in the Brachionus plicatilis species complex range at least from 0.056 to 0.416 pg.Stelzer CP, Riss S and Stadler P. (2011): Genome size evolution at the speciation level: the cryptic species complex Brachionus plicatilis (Rotifera). BMC Evol Biol. 2011 Apr 7;11:90.
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Sterile water samples have been observed to be less susceptible to speciation changes than non-sterile samples. Oremland found that the reduction of As(V) to As(III) in Mono Lake was rapidly catalyzed by bacteria with rate constants ranging from 0.02 to 0.3 day−1.
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This region is largely bypassed by the Agulhas current, and has cooler inshore water due to upwelling, making it less hospitable to tropical Indo-west Pacific species. It is also isolated from the South Atlantic and Southern Ocean, so has been more prone to niche speciation.
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The Australian species of Camphorosmeae form a relatively young group still in the process of speciation and with some hybridization between species. In phylogenetic research by Cabrera et al. (2009), the genera were not clearly separated. Probably Neobassia, Threlkeldia and Osteocarpum should be included in Sclerolaena.
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This region is largely bypassed by the Agulhas current, and has cooler inshore water due to upwelling, making it less hospitable to tropical Indo-west Pacific species. It is also isolated from the South Atlantic and Southern Ocean, so has been more prone to niche speciation.
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The secondary contact of originally separated incipient species (the initial stage of speciation) is increasing due to human activities such as the introduction of invasive species or the modification of natural habitats. This has implications for measures of biodiversity and may become more relevant in the future.
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S. perpusillum is a tropical species endemic to southwestern, Western Australia and is considered to be the smallest species in the genus Stylidium.Carlquist, S.J. (1979). Stylidium in Arnhem land: New species, modes of speciation on the sandstone plateau, and comments on floral mimicry. Aliso, 9: 411-461.
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Strophocincla laughingthrushes of south India: a case for allopatric speciation and impact on their conservation. Journal of the Bombay Natural History Society 109(1–2): 46–52. and the Banasura laughingthrush was consequently awarded full species status in 2015.del Hoyo, J., and N. J. Collar (2016).
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Speciation through natal philopatry is a self-reinforcing process. Once genetic differences are sufficient, different species may be unable to interbreed to produce viable offspring. As a result, breeding could not occur anywhere except natal island, strengthening philopatry and ultimately leading to even greater genetic divergence.
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Stocking, p. 251. On the topic of race, the Ethnological Society retained views descending from Johann Friedrich Blumenbach, who had a five-race theory but was a monogenist, and from Prichard. The post-Darwin concept of human speciation was unacceptable to those forming the Anthropological Society.
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Moreover, speciation determines how to control mercury emissions to air. For example, emissions of inorganic mercuric compounds (such as mercuric chloride) are captured reasonably well by some control devices (such as wet-scrubbers), while capture of elemental mercury tends to be low for most emission control devices.
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M. castrator is directly descended from M. goeldii, its host. Such relationships are not uncommon among social parasites, as recognized by Emery's rule. Less common are cases like M. castrator's, where two species diverge without the benefit of geographic isolation, known as sympatric speciation. Rabeling et al.
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Other biota found in the Phantom Lake Spring include the snails Pyrgulopsis texana and Lyrodes cheatumi. The absence of Hyalella azteca may have allowed speciation to take place in the genus Gammarus, with one species entering the vacant niche, and reducing in size to become G. hyalelloides.
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In addition to the main operators above, other heuristics may be employed to make the calculation faster or more robust. The speciation heuristic penalizes crossover between candidate solutions that are too similar; this encourages population diversity and helps prevent premature convergence to a less optimal solution.
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Postcranial measurements and anatomy suggest that three of the four genera, Palaeopropithecus, Babakotia, and Mesopropithecus were primarily arboreal and suspensory. The family was isolated due to river systems which formed a bio- geographical boundary, and likely attributed to the speciation of the family into four genera.
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Much later, the biologist Ernst Mayr was the first to encapsulate the then contemporary literature in his 1942 publication Systematics and the Origin of Species, from the Viewpoint of a Zoologist and in his subsequent 1963 publication Animal Species and Evolution. Like Jordan's works, they relied on direct observations of nature, documenting the occurrence of allopatric speciation, of which is widely accepted today. Prior to this research, Theodosius Dobzhansky published Genetics and the Origin of Species in 1937 where he formulated the genetic framework for how speciation could occur. Other scientists noted the existence of allopatrically distributed pairs of species in nature such as Joel Asaph Allen (who coined the term "Jordan's Law", whereby closely related, geographically isolated species are often found divided by a physical barrier) and Robert Greenleaf Leavitt; however, it is thought that Wagner, Karl Jordan, and David Starr Jordan played a large role in the formation of allopatric speciation as an evolutionary concept; where Mayr and Dobzhansky contributed to the formation of the modern evolutionary synthesis.
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Molecular phylogeny and systematics of Neotropical toucanets in the genus Aulacorhynchus (Aves, Ramphastidae). Zoologica Scripta, 40. Puebla-Olivares, F., E. Bonaccorso, A. E. de los Monteros, K. E. Omland, J. E. Llorente-Bousquets, A. T. Peterson, and A.G. Navarro-Siguenza. (2008). Speciation in the Emerald Toucanet (Aulacorhynchus prasinus) complex.
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The second phase is marked by long term adaptations to the local environment. In this period, abilities for dispersal are commonly reduced, and colonizers will either differentiate or assimilate with competing species. In the third phase, the evolution of colonizing populations may result in speciation and/or adaptive radiation.
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Some consider the observations in Louisiana to be of F. hathawayi or F. h. blacki and not F. maletae. Phylogenetic study of the Texas populations indicate they are distinct genetically, perhaps even a separate cryptic species. The populations also inhabited separate ecological niches, which may further drive speciation.
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Polistes fuscatus, whose common name is the golden or northern paper wasp, is widely found throughout southern Canada, the United States, Mexico, and Central America.Metcalf, R.A.; J.C. Marlin; and G. S. Whitt. (1984). Genetics of Speciation within the Polistes fuscatus Species Complex. The Journal of Heredity 117-20. Print.
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In this case insects become specialized as they struggle to overcome the various plants' defense mechanisms. (Drès and Mallet, 2002)Begon, Townsend, Harper: Ecology – From individuals to ecosystems, 4th ed., p.10 Rhagoletis pomonella, the apple maggot, may be currently undergoing sympatric or, more precisely, heteropatric (see heteropatry) speciation.
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Another example of protein speciation is the case of the frog where Xnr1 and Xnr2 regulate movements in gastrulation in contrast to Xnr5 and Xnr6 that are involved in mesoderm induction. In mouse, Nodal has been implicated in left-right asymmetry, neural pattering and mesoderm induction (see nodal signaling).
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This earthworm is tolerant of soils with high levels of heavy metals and toxic semimetals. It has been observed in mine spoils contaminated with arsenicLangdon, C. J., et al. (2003). Arsenic speciation in the earthworms Lumbricus rubellus and Dendrodrilus rubidus. Environmental Toxicology and Chemistry 22(6), 1302-08.
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Humans have also changed species compositions of many landscapes that they do not dominate directly by introducing new species or harvesting native species. This new assemblage of species has been compared to previous mass extinctions and speciation events caused by formation of land bridges and colliding of continents.
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The authors of this study concluded that speciation was discernible. In another study concerning morphological trends and rates of evolution found that the European arvicolid rodent radiated into 52 distinct lineages over a time frame of 5 million years while documenting examples of phyletic gradualism, punctuation, and stasis.
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The highly focused and intense beams study small spots on biological samples allowing analysis to micro level along with the chemical speciation. In a study, this method has been used to follow arsenic level before, during and after treatment with arsenious oxide in patients with acute promyelocytic leukemia.
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In: Llorente J. Morrone, J.J. (Eds.) Una perspectiva latinoamericana de la biogeografía Universidad Autónoma de México, México. Preliminary analysis suggest that the genus is monophyletic, and the speciation sequence seems to correspond to the sequence of up-lifting and separation of the páramo biome in recent geological times.
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Presgraves' work has contributed to the current understanding of sexual selection, meiotic drive, and the X-Chromosome's evolutionary importance. His work has led to the confirmation of a phenomenon called the "large X-effect," which describes the integral role of the X-Chromosome as a wedge in driving speciation.
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Inocybe is a large genus of mushroom-forming fungi with over 1400 species, including all forms and variations. Members of Inocybe are mycorrhizal, and some evidence shows that the high degree of speciation in the genus is due to adaptation to different trees and perhaps even local environments.
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434x434px The fossil record includes well documented examples of both phyletic gradualism and punctuational evolution. As such, much debate persists over the prominence of stasis in the fossil record.Erwin, D. H. and R. L. Anstey (1995) New approaches to speciation in the fossil record. New York : Columbia University Press.
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On the engine of speciation. J. theor. Biol. 177, 401-409 Evidence for stasis has also been corroborated from the genetics of sibling species, species which are morphologically indistinguishable, but whose proteins have diverged sufficiently to suggest they have been separated for millions of years.Maynard Smith, John (1989).
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Bromine can substitute for some chlorine, forming brominated trihalomethanes. Because bromine has a higher atomic weight than chlorine, the partial conversion to brominated trihalomethanes increases the concentration by weight of total trihalomethanes.Paul Handke, Trihalomethane speciation and the relationship to elevated total dissolved solid concentrations, Pennsylvania Department of Environmental Protection.
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New species arise through the process of speciation, an aspect of evolution. New varieties of organisms arise and thrive when they are able to find and exploit an ecological niche – and species become extinct when they are no longer able to survive in changing conditions or against superior competition.
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It includes the study of genetic change and the consequent variation that often results in speciation, one of the most important types of radiation into taxonomic groups called clades. A description of radiation is called a phylogeny and is often represented by type of diagram called a phylogenetic tree.
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Clownfish and sea anemones are one of the most compelling cases of symbiosis. The relationship provides mutual protection from predators and the exchange of nutrients. Divergent natural selection drives adaptive diversification through ecological speciation. The ability of clownfish to use sea anemones as hosts has evolved 4 independent times.
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Corliss' CA model of evolution. Vertical axis represents time, horizontal axes represent speciation. In 1988, Corliss joined the NASA Goddard Space Flight Center's high-performance computing division. There he began using massively parallel computers (the Goodyear MPP and later MasPar MP-1) for cellular automata simulations of evolutionary systems.
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A paleoecological model for conodont speciation during the Permian. Geological Society of America, Abstracts with Programs (7): 720-721 Wardlaw and Collinson (1984) proposed that Hindeodus dominated in lagoonal facies.B.R. Wardlaw, J.W. Collinson. 1984. Conodont paleoecology of the Permian Phosphoria Formation and related rocks of Wyoming and adjacent area.
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Genetic analysis performed on this species suggest that it evolved directly from Layia glandulosa in what may be an example of both allopatric speciation and peripatric speciation.Baldwin, B. G. (2005). Origin of the serpentine-endemic herb Layia discoidea from the widespread L. glandulosa (Compositae). Evolution 59:11 2473-79.
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Thus, species associations can lead to rapid diversification of both lineages and contribute to overall community diversity. Ecological fitting can also maintain populations in stasis, influencing diversity by limiting it. If populations are well connected through gene flow, local adaptation may not be able to occur (known as antagonistic gene flow), or the well-connected population could evolve as a whole without speciation occurring. The Geographic Mosaic of Coevolution theory can help to explain this: it suggests that coevolution or speciation of a species occurs across a wide geographic scale, rather than at the level of populations, so that populations experiencing selection for a particular trait affect gene frequencies across the geographic region due to gene flow.
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Many species of the carolinensis subgroup are remarkably obscure and, with the exception of a few species such as A.carolinensis, very little is known about its members or its origin. However, it is believed that the clade originated on Cuba (Glor 2005), with repeated overwater dispersion leading to multiple speciation events. It is believed that at least four separate speciation events would have been necessary to explain the diversity found within the Carolinensis subgroup; however, the origin of several species such as A.longiceps, A.brunneus and A.maynardi has not been fully understood. It is believed that the last common ancestor of the Carolinensis subgroup evolved approximately six million years ago; molecular dating currently supports this theory.
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Genetic exchange can occur between populations or incipient species diverging in geographical proximity or between divergent taxa that come into secondary contact. Hybridization between more diverged lineages is expected to have a greater potential to contribute beneficial alleles or generate novelty than hybridization between less diverged populations because more divergent alleles are combined, and are thus more likely to have a large fitness effect, to generate transgressive phenotypes. Hybridization between more diverged lineages is also more likely to generate incompatible allele combinations, reducing initial hybrid fitness but potentially also contributing to hybrid speciation if they are sorted reciprocally as described above. An intermediate genetic distance may thus be most conducive to hybrid speciation.
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Ernst Mayr, an influential evolutionary biologist In 1947, "a consensus had been achieved among geneticists, paleontologists and systematists and that evolutionary biology as an independent biological discipline had been established" during a Princeton University conference. This 20th century synthesis incorporated speciation. Since then, the ideas have been consistently and repeatedly confirmed.
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The larvae feed on various plants, including Brachypodium sylvaticum, Agrostis capillaris, Carex divulsa and Luzula forsteri. It is closely related to the species Pararge aegeria.Weingarter, Wahlberg & Nylin (2006): Speciation in Pararge (Satyrinae: Nymphalidae) butterflies - North Africa is the source of ancestral populations of all Pararge species. Systematic Entomology 31: 621-632.
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It is hypothesized that P. femoralis has diverged to form P. robinsoni and P. siamensis. Both species are monoplyletic compared to P. femoralis. The movement of P. femoralis to the Malaysian peninsula created the allopatric distribution. Further dispersal on the peninsula itself diverged P. robinsoni and P. siamensis through allopatric speciation.
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Young orangutan at Bukit Lawang, Sumatra Tropical rainforests exhibit a vast diversity in plant and animal species. The root for this remarkable speciation has been a query of scientists and ecologists for years. A number of theories have been developed for why and how the tropics can be so diverse.
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In addition to his work in phylogenetics, Felsenstein is also noted for his work in theoretical population genetics, including studies on selection, migration, linkage, speciation, and the coalescent.Felsenstein, J., and B. Taylor, eds. 1973. A Bibliography of Theoretical Population Genetics. U.S. Atomic Energy Commission, Technical Information Center, Oak Ridge, Tenn.
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S. eminens is a tetraploid, resulting from hybridisation between Sorbus aria and Sorbus porrigentiformisRobertson, A., Rich, T.C., Allen, A.M., Houston, L., Roberts, C.A.T., Bridle, J.R., Harris, S.A. and Hiscock, S.J., 2010. Hybridization and polyploidy as drivers of continuing evolution and speciation in Sorbus. Molecular Ecology, 19(8), pp.1675-1690.
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Caecosagitta macrocephala is a deep sea marine chaetognath that is distributed in meso- and bathypelagic layers. It has a very wide distribution that ranges from the Subantarctic to Subarctic Ocean. Miyamoto, H., Machida, R. & Nishida, S. (2010). Genetic diversity and cryptic speciation of the deep-sea chaetognath Caecosagitta macrocephala (Fowler, 1904).
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Any splitting of a single population of individuals into discrete parts may be considered fission. A population may undergo fission for a variety of reasons, including migration or geographic isolation. Because the fission leads to genetic variance in the newly isolated, smaller populations, population fission is a precursor to speciation.
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The colour polymorphism of female Zootoca vivipara has not been thoroughly studied in past years, regardless of the extensive research done on the species itself.Svensson, E.I., Abbott, J., Gosden, T., Coreau, A. 2009. Female polymorphisms, sexual conflict, and limits to speciation processes in animals. Behavioral Evology 23(1) 93-108.
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The telomeric sync model of speciation: species-wide telomere erosion triggers cycles of transposon-mediated genomic rearrangements, which underlie the saltatory appearance of nonadaptive characters. Naturwissenschaften 101: 163-186. He was a proponent of National Socialist ideology and wrote about the Aryan race. He was director of the Zoologische Staatssammlung München.
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The various lifestyles of icefish are thought to have caused speciation within the family. For example, blackfin icefish adults have a very sedentary lifestyle, which may have geographically isolated them from other members of the family. Other species, such as Champsocephalus gunnari, are more pelagic and seem to have avoided isolation.
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This glossary of evolutionary biology is a list of definitions of terms and concepts used in the study of evolutionary biology, population biology, speciation, and phylogenetics, as well as sub-disciplines and related fields. For additional terms from related glossaries, see Glossary of genetics, Glossary of ecology, and Glossary of biology.
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Transactions of the British Mycological Society, 63(OCT): 391-393. Since this pathogen affects trees, orchards are very susceptible to infection due to the genetic uniformity of the plants therein.Slippers, B., G. Fourie, P.W. Crous, T.A. Coutinho, B.D. Wingfield, A.J. Carnegie and M.J. Wingfield, 2004. Speciation and distribution of botryosphaeria spp.
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Gene conversion and linkage: Effects on genome evolution and speciation. Molecular Ecology, 26: 351-364. doi:10.1111/mec.13736. abs #McGaugh, S. E., C. S. S. Heil, B. Manzano-Winkler, L. Loewe, S. Goldstein, T. L. Himmel, M. A. F. Noor. 2012. Recombination modulates how selection affects linked sites in Drosophila.
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In addition, parasitic (cuckoo) bumblebees resemble their hosts more closely than would be expected by chance, at least in areas like Europe where parasite-host co-speciation is common; but this too may be explained as Müllerian mimicry, rather than requiring the parasite's coloration to deceive the host (aggressive mimicry).
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In the present, M. fulvum is still referred to as part of the Microsporum gypseum complex. This complex includes the three distinct species: Microsporum gypseum, Microsporum fulvum and Microsporum incurvatum. Each of these fungi possess a high degree of morphological similarity but do have significant genetic differences accounting for the speciation.
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In this way, hybrid infertility contributes in some part to speciation by ensuring that gene flow between diverging species remains limited. Further analysis of the issue has supported this model, although it does not include conspecific genic interactions, an potential factor that more recent research has begun to look in to.
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Albert, E. M., R. Zardoya, and M. García- París. "Phylogeographical and Speciation Patterns in Subterranean Worm Lizards of the Genus Blanus (Amphisbaenia: Blanidae)." Molecular Ecology 16.7 (2007): 1519-531. Print. While little is known of B. cinereus in comparison with some other reptile species, new insight is growing about this primitive, ancestral reptile.
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Archana Sharma was a renowned Indian botanist, cytogeneticist, cell biologist, and cytotoxicologist. Her widely recognized contributions include the study of speciation in vegetatively reproducing plants, induction of cell division in adult nuclei, the cause of polyteny in differentiated tissues in plants, cytotaxonomy of flowering plants, and the effect of arsenic in water.
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The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.Strickberger, M. 1978. Genética.
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Brush-furred mice are solitary and are reported to fight when placed together. This may contribute to the wounds found on individuals. A brush-furred mouse was recorded to have lived for over 3 years in captivity. Allopatric speciation appears to have played an important role in shaping the evolution of this genus.
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But not as many as Central Asia: the former USSR has twice as many. The plasticity of this genus is astonishingly high. Depending on environmental conditions a big variety of life-forms evolved, ranging from tiny annuals to small woody and thorny bushes. Speciation seems to be in plain progress in Astragalus.
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Deltaretroviruses only affect mammals, and this was the first evidence that they affected bat species. The presence of the deltaretrovirus in multiple Miniopterid species suggests that the virus was present in the family before speciation 20 million years ago. The evolutionary history of deltaretroviruses is important because they cause leukemia in humans.
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Polyploidy is also a well known source of speciation, as offspring, which have different numbers of chromosomes compared to parent species, are often unable to interbreed with non-polyploid organisms. Whole genome duplications are thought to be less detrimental than aneuploidy as the relative dosage of individual genes should be the same.
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It is important to note that the 3 sub-mechanisms: dispersal, competition and energetic restraints must in some manner feed back into either speciation or extinction rates as these are the only ultimate processes (see Tinbergen's four questions) governing the number of species on earth and hence the body size-species richness pattern.
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Similarly, a study using birds failed to demonstrate that body size and speciation rates were negatively correlated (Nee et al. 1992Nee S, Mooers A & Harvey P (1992) Tempo and mode of evolution revealed from molecular phylogenies. Proceedings of the National Academy of Sciences of the United States of America 89(17):8322-8326.).
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Most estimates from studies of nature indicate that speciation takes hundreds of thousands to millions of years. On the other hand, many species are thought to have speciated faster and more recently, such as the European flounders (Platichthys flesus) that spawn in pelagic and demersal zones—having allopatrically speciated in under 3000 generations.
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These characteristics are genetically inherited and has been interpreted as the early stages of the speciation process. The two ecotypes will eventually become separate species once reproductive isolation is achieved. At the moment, both ecotypes are still capable of interbreeding and producing viable offspring, as such they are still considered a single species.
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McCarthy, T. & Rubridge, B. (2005) The Story of Earth and Life. Cape Town: Struik Publishers. . including a meta-analysis examining 58 published studies on speciation patterns in the fossil record showed that 71% of species exhibited stasis, and 63% were associated with punctuated patterns of evolutionary change.Erwin, D.H. and Anstey, R.L (1995).
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Female frogs choose a mate based on the attractiveness of a male's call. The females are able to recognize the species of the calling maleRyan, Michael, and Monica Guerra. (2014). The Mechanism of Sound Production in Tungara Frogs and Its Role in Sexual Selection and Speciation. Current Opinion in Neurobiology 28: 54-59.
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The botanist G. Ledyard Stebbins extended the synthesis to encompass botany. He described the important effects on speciation of hybridization and polyploidy in plants in his 1950 book Variation and Evolution in Plants. These permitted evolution to proceed rapidly at times, polyploidy in particular evidently being able to create new species effectively instantaneously.
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The interfertility of human races was debated, applying to human speciation arguments advanced already by Georges- Louis Leclerc, Comte de Buffon. The criterion of interfertility for a single human species was not universally accepted, being rejected, for example, by Samuel George Morton.Elise Lemire, Miscegenation: Making Race in America (2009), p. 113; Google Books.
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It diverged from a common ancestor with Poncirus trifoliata. A change in climate conditions during the Late Miocene (11.63 to 5.33 mya) resulted in a sudden speciation event. The species resulting from this event include the citrons (Citrus medica) of South Asia; the pomelos (C. maxima) of Mainland Southeast Asia; the mandarins (C.
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Speciation diagram for a 10-millimolar solution of citric acid. The violet curve corresponds to the trisodium citrate. As a conjugate base of a weak acid, citrate can perform as a buffering agent or acidity regulator, resisting changes in pH. It is used to control acidity in some substances, such as gelatin desserts.
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The evidence for speciation in this case was morphology (physical appearance) and lack of natural interbreeding. These fish have complex mating rituals and a variety of colorations; the slight modifications introduced in the new species have changed the mate selection process and the five forms that arose could not be convinced to interbreed.
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Over a long time, only a single species of placozoan clades,Trichoplax adhaerens, was described but lately, it has been found that the relatively newer species, 'Hoilungia hongkongensis' is a result of reproductive isolation mechanism of speciation. Francis, Warren R., et al. “Comparative Genomics and the Nature of Placozoan Species.” PLoS Biology.
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The neutral theory of molecular evolution is an important and often controversial theory proposing that most molecular variation within and among species is essentially neutral and not acted on by selection. Neutral mutations are also the basis for using molecular clocks to identify such evolutionary events as speciation and adaptive or evolutionary radiations.
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He was the Professor of Botany for the University of Texas at Austin from 1970 to 1987."Verne Grant". ASPT Newsletter 21(1): 3-4. 2007. His book The Origins of Adaptations (1963) discussed the main themes of the modern synthesis such as genetic drift, modes of speciation, natural selection and population genetics.
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Systematics of Juniperus section Juniperus based on leaf essential oils and RAPD DNA fingerprinting. Biochem. Syst. Ecol. 28: 515-528. available online (pdf file)Adams, R. P., Morris, J. A., Pandey, R. N., & Schwarzbach, A. E. (2005). Cryptic speciation between Juniperus deltoides and J. oxycedrus (Cupressaceae) in the Mediterranean. Biochem. Syst. Ecol.
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Scientists observing the patterns of a species biogeographic distribution and its phylogenetic relationships are able to reconstruct the historical process by which they diverged. Further, oceanic islands are often the subject of peripatric speciation research due to their isolated habitats—with the Hawaiian Islands widely represented in much of the scientific literature.
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Andre M. N. Silva, XiaoLe Kong, Mark C. Parkin, Richard Cammack and Robert C. Hider (2009): "Iron(III) citrate speciation in aqueous solution". Royal Chemical Society, Dalton Transactions, pages 8616-8625. At physiological pH, ferric citrate forms an insoluble red polymer. In other conditions, it forms anionic complexes like []2()2]2−.
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Frank Harlan Lewis (January 8, 1919 – December 12, 2008) ("Harlan Lewis") was an American botanist, geneticist, taxonomist, systematicst, and evolutionist who worked primarily with plants in the genus Clarkia. He is best known for his theories of "Catastrophic Selection," and "Saltational Speciation", which are closely aligned with the concepts of quantum evolution and sympatric speciation. The concepts were first articulated in 1958 by Harlan Lewis and Peter H. Raven, and later refined in a 1962 paper by Lewis in which he coined the term "Catastrophic Selection;" in 1966 he called this mechanism "Saltational Speciation." He was Dean of Life Sciences at the University of California, Los Angeles from 1962 to 1981, a Fellow of the American Association for the Advancement of Science (1955), he was awarded a Guggenheim Fellowship (1955), president of the Pacific Division of the Botanical Society of America (1959), president of Society for the Study of Evolution (1961), president of the American Society of Plant Taxonomists (1969), president of the International Organization of Plant Biosystematics (1969–1975), and president of the American Society of Naturalists (1971), as well as a Fellow of the California Academy of Sciences.
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Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often after the populations have become reproductively isolated for some period of time. In some cases, subpopulations living in ecologically distinct peripheral environments can exhibit genetic divergence from the remainder of a population, especially where the range of a population is very large (see parapatric speciation). The genetic differences among divergent populations can involve silent mutations (that have no effect on the phenotype) or give rise to significant morphological and/or physiological changes. Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal mechanism underlying speciation.
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Punctuated gradualism is a microevolutionary hypothesis that refers to a species that has "relative stasis over a considerable part of its total duration [and] underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching". It is one of the three common models of evolution. While the traditional model of palaeontology, the phylogenetic model, states that features evolved slowly without any direct association with speciation, the relatively newer and more controversial idea of punctuated equilibrium claims that major evolutionary changes don't happen over a gradual period but in localized, rare, rapid events of branching speciation. Punctuated gradualism is considered to be a variation of these models, lying somewhere in between the phyletic gradualism model and the punctuated equilibrium model.
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660x660px If we consider a rooted three-taxon tree, the simplest non-trivial phylogenetic tree, there are three different tree topologies but four possible gene trees. The existence of four distinct gene trees despite the smaller number of topologies reflects the fact that there are topologically identical gene tree that differ in their coalescent times. In the type 1 tree the alleles in species A and B coalesce after the speciation event that separated the A-B lineage from the C lineage. In the type 2 tree the alleles in species A and B coalesce before the speciation event that separated the A-B lineage from the C lineage (in other words, the type 2 tree is a deep coalescence tree).
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Two distinct, but closely related species exist on the same island, but they occupy two distinct soil types found on the island, each with a drastically different pH balance. Because they are palms they send pollen through the air they could freely interbreed, except that speciation has already occurred, so that they do not produce viable hybrids. This is hard evidence for the fact that, in at least some cases, fully sympatric species really do experience diverging selection due to competition, in this case for a spot in the soil. This, and the other few concrete examples that have been found, are just that; they're few, so they tell us little about how often sympatry actually results in speciation in a more typical context.
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Although some evolutionary biologists still regard sympatric speciation as highly contentious, both theoretical and empirical studies support it as a likely explanation of the diversity of life in particular ecosystems. Arguments implicate competition and niche separation of sympatric ecological variants that evolve through assortative mating into separate races and then species. Assortative mating most easily occurs if mating is linked to niche preference, as occurs in the apple maggot Rhagoletis pomonella, where individual flies from different races use volatile odors to discriminate between hawthorn and apple and look for mates on natal fruit. The term heteropatry semantically resolves the issue of sympatric speciation by reducing it to a scaling issue in terms of the way the landscape is used by individuals versus populations.
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Oxbow River Formation River barrier speciation occurs when a river is of sufficient size to provide a vicariance for allopatric speciation, or when the river is large enough to prevent or interfere with a genetic exchange between populations. Population division is initiated either when a river shifts into or forms within the range of a species that cannot cross it, effectively splitting the population in half, or when a small founder group is transported across an existing river through random chance. Usually a river's strength as a barrier is viewed as proportional to its width; wider rivers present a longer crossing distance and thus a greater obstacle to movement. Barrier strength varies within a given river; narrow headwaters are easier to cross than wide downstream channels.
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Known examples of ecological speciation are three- spined stickleback fishes, distinct species of which emerged as the result of adaptation to different conditions along water depth clines in freshwater lakes. Ancestors of the genus Ilex (holly) became isolated from the remaining Ilex when the landmass broke up into Gondwana and Laurasia about 82 million years ago, resulting in a physical separation of the groups (allopatry) and beginning its adaptation to new conditions; over time survivor species of the holly genus adapted to different ecological niches. The invasive weed species Centaurea solstitialis is thought to be a case of ecological speciation—in less than 200 years, incipient reproductive isolation appeared as a result of adaptation to differences in ecological conditions between native and non- native ranges.
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Conversely, zoologist Michael J. D. White considered two populations sympatric if genetic interbreeding was viable within the habitat overlap. This may be further specified as sympatry occurring within one deme; that is, reproductive individuals must be able to locate one another in the same population in order to be sympatric. Others question the ability of sympatry to result in complete speciation: until recently, many researchers considered it nonexistent, doubting that selection alone could create disparate, but not geographically separated, species. In 2003, biologist Karen McCoy suggested that sympatry can act as a mode of speciation only when "the probability of mating between two individuals depend[s] [solely] on their genotypes, [and the genes are] dispersed throughout the range of the population during the period of reproduction".
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Mayr emphasized the importance of allopatric speciation, where geographically isolated sub-populations diverge so far that reproductive isolation occurs. He was skeptical of the reality of sympatric speciation believing that geographical isolation was a prerequisite for building up intrinsic (reproductive) isolating mechanisms. Mayr also introduced the biological species concept that defined a species as a group of interbreeding or potentially interbreeding populations that were reproductively isolated from all other populations. Before he left Germany for the United States in 1930, Mayr had been influenced by the work of the German biologist Bernhard Rensch, who in the 1920s had analyzed the geographic distribution of polytypic species, paying particular attention to how variations between populations correlated with factors such as differences in climate.
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Such a transition is called anagenesis; he posited that, if the opposite, cladogenesis, could not be proven, a scientist was free to assume an anagenetic process. Basing himself on revised data, Sampson in 1995 estimated that the layers investigated represented a longer period of time than the initially assumed 500,000 years: after the deposition of Gilmore's Brachyceratops quarry, 860,000 years would have passed, and after the Einiosaurus beds 640,000 years, until the maximal extent of the Bearpaw transgression. He did not adopt Horner's hypothesis of anagenesis but assumed speciation took place, with the populations splitting. These time intervals were still short enough to indicate that the rate of speciation must have been high, which might have been true of all centrosaurines of the late Campanian.
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S. saturatus occurs in the northwestern United States, north of the Columbia River, south of the Tulameen River in British Columbia, and west of the Similkameen River. No fossils have yet been found. S. saturatus is isolated from its sister species S. lateralis by the Columbia River; their differentiation is likely due to allopatric speciation.
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Page is known for his work on co-speciation and in particular the development of bioinformatic software such as TreeMap, RadCon, and TreeView. Page is a co-author with Eddie Holmes of Molecular Evolution: A phylogenetic approach and editor of Tangled trees: phylogeny, cospeciation and coevolution.Page, R.D.M. ed. (2002). Tangled trees: phylogeny, cospeciation and coevolution.
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Der Züchter. 5: 133–140. German abstract available G. D. Karpechenko specialized in plant cytology and created several hybrids. Among his contributions is his seminal work on allopolyploids, culminating in his creation of a fertile offspring of radishes and cabbages, the first instance of a new species obtained through polyploid speciation during experimental crossbreeding.
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Encke, Stuttgart, 1954. for example, stated that evolutionary rates also depend on temperature: numbers of generation in poikilotherms, but sometimes also in homoiotherms (homoiothermic), are greater at higher temperatures and the effectiveness of selection is therefore greater. Ricklefs refers to this hypothesis as "hypothesis of evolutionary speed" or "higher speciation rates".R.E. Ricklefs: Ecology.
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Proceedings: Biological Sciences 277, 885–94 (2010). While sexual coercion does help increase male fitness, it is very often costly to females. Sexual coercion has been observed to have consequences, such as intersexual coevolution, speciation, and sexual dimorphism.Rönn, J., Katvala, M. & Arnqvist, G. Coevolution between harmful male genitalia and female resistance in seed beetles.
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Patella aspera is a species of limpet, a type of sea snail in the family Patellidae. Long considered to be a subspecies of Patella ulyssiponensis, genetic evidence supports its recognition as a separate species.Weber, L. I., and S. J. Hawkins. (2005). Patella aspera and P. ulyssiponensis: genetic evidence of speciation in the North-east Atlantic.
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Each group member is found in hot, arid regions with low rainfall. They prefer soil that is loose, gravelly, and well-drained. C. cordata is found only in the vicinity of Bahía de los Ángeles, Baja California. Botanists Bemis and Whitaker suggest that C. cordata and C. cylindrata may be a case of sympatric speciation.
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African cichlids also offer some evidence for sympatric speciation. They show a large amount of diversity in the African Great Lakes. Many studies point to sexual selection as a way of maintaining reproductive isolation. Female choice with regards to male coloration is one of the more studied modes of sexual selection in African cichlids.
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Tarkhnishvili DN (2012) Evolutionary History, Habitats, Diversification, and Speciation in Caucasian Rock Lizards. In: Advances in Zoology Research, Volume 2 (ed. Jenkins OP), Nova Science Publishers, Hauppauge (NY), p.79-120 This genus is unique in containing the only known monoclonal parthenogenetic species, Lacerta rostombekovi, where the entire species originates from a single hybridization event.
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This information is vital in order to improve our understanding of connectivity between seamount hotspots and adjacent areas, and HERMIONE research will aim to discover whether seamounts act as centres of speciation (the evolution of new species), or if they play a role as "stepping stones", allowing fauna to colonise and disperse across the oceans.
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It is found in the Americas from Argentina and Peru north to Mexico, and Cuba. Populations in Florida in the United States are now recognized as the Florida bonneted bat (E. floridanus.)McDonough, M. M., et al. (2008). Speciation within bonneted bats (genus Eumops): the complexity of morphological, mitochondrial, and nuclear data sets in systematics.
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Homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event (orthologs) or a duplication event (paralogs). Homologs are similar genes and/or proteins which are related by ancestry. Orthologs are the 'same' gene, but from different organisms.
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An alternative or simultaneous reaction is the substitution of Cl− with Br− about the Au(III) center. Both complexation with the ammonium cation and/or speciation of the Au(III) precursor influence the kinetics of the nanoparticle formation reaction and therefore influence the size, shape, and (size and shape) distributions of the resulting particles.
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In: M. Hotta (ed.) Diversity and Dynamics of Plant Life in Sumatra: Forest Ecosystem and Speciation in Wet Tropical Environments. Part 1: Reports and Collection of Papers. Kyoto University, Kyoto. pp. 75–109. Matthew Jebb also treated N. sumatrana separately in his 1991 monograph, "An account of Nepenthes in New Guinea",Jebb, M.H.P. 1991.
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Those remaining actinosporeans whose myxosporean stage is unattested are being retained as species inquerandae until their specific identity is established. It has been hypothesized that myxosporeans might have evolved from a transmissible tumor of Polypodium. This hypothesis is called the "SCANDAL hypothesis", an acronym for speciation by cancer development animals, referencing its radical nature.
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This promotes divergence due to strong selective pressures, leading to the rapid fixation of an allele within the descendant population. This gives rise to the potential for genetic incompatibilities to evolve. These incompatibilities cause reproductive isolation, giving rise to rapid speciation events. Models of peripatry are supported mostly by species distribution patterns in nature.
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Littorina saxatilis has been shown to be an excellent model system for speciation genetics. In the seminal 2001 paper, Wilding et al demonstrated, using amplified fragment length polymorphism, that the low shore M form of the species were divergent from the high shore H form at number of loci despite gene flow between the forms.
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Stomatepia is a genus of cichlids endemic to Lake Barombi Mbo in western Cameroon. Although generally recognized as distinct, the genus is very close to Sarotherodon.Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation.
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Characteristic quantities for water solutions such as solubilities, equilibrium constants, activity coefficients, heat capacities and densities can be calculated from changes in the chemical speciation. Recent examples of practical problems that can be investigated by JESS include kidney stones (mineral precipitation and dissolution in the kidney) and Wilson’s disease (copper physiology in the human eye).
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These species include Otus longicornis, Otus mindorensis, Otus mirus, Otus magalotis and Otus fuliginosus. The other two species, Otus mantananensis and Otus elegans are not endemic to the Philippines. The three Otus megalotis subspecies are distributed among different islands of the Philippine Archipelago which suggests they could have evolved through speciation from geographic isolation.
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Sukumar, pp. 24–27. At the beginning of the Pleistocene, elephantids experienced a high rate of speciation. The Pleistocene also saw the arrival of Palaeoloxodon namadicus, the largest terrestrial mammal of all time. Loxodonta atlantica became the most common species in northern and southern Africa but was replaced by Elephas iolensis later in the Pleistocene.
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Eriogonum is the scientific name for a genus of flowering plants in the family Polygonaceae. The genus is found in North America and is known as wild buckwheat. This is a highly species-rich genus, and indications are that active speciation is continuing. It includes some common wildflowers such as the California buckwheat (Eriogonum fasciculatum).
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M. J. Littlejohn (1981). Reproductive isolation: A critical review. In W. R. Atchley and D. S. Woodruff (eds) Evolution and Speciation, Cambridge University Press, Pp. 298–334. Theodosius Dobzhansky was the first to provide a thorough description of the process in 1937, though the term itself was not coined until 1955 by W. Frank Blair.
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A Chorus Frog making a mating call Several studies have shown that the species Pseudacris triseriata (Chorus Frog) can be divided into two subspecies, P. t. maculata and P. t. triseriata, due to speciation events from mating call differences. The Chorus Frog has a very large home range, from New Mexico to Southern Canada.
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The Distribution of Chemical Elements in Sponges of the Family Lubomirskiidae in Lake Baikal. International Symposium - Speciation in Ancient Lakes, SIAL III - Irkutsk 2002. Berliner Paläobiologische Abhandlungen 4: 151-157. Lubomirskia baikalensis is found on hard bottoms of shallow water at depths between Kaluzhnaya; Belikov; Schröder; Rothenberger; Zapf; Kaandorp; Borejko; Müller; and Müller (2005).
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Michael Ritchie is a British evolutionary biologist and professor at the University of St Andrews. He is known for his work on speciation. He served as editor-in-chief of the Journal of Evolutionary Biology from 2011 to 2017, and Vice-President of the Society for the Study of Evolution from 2004 to 2005.
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Durrant's 1952 book Mammals of Utah: Taxonomy and Distribution presented taxonomic synopses of 247 species and subspecies of Utah mammals, as well as Durrant's explanations for the origins of such diversity: largely that the geographic and hydrological history of the region, especially the prehistoric Lake Bonneville, promotes reproductive isolation and subsequent speciation or subspeciation.
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The ancestor of Euchiloglanis originated from the allied Glyptosternon in the second uplift and Pareuchiloglanis, Pseudexostoma, Oreoglanis, Exostoma, and Glaridoglanis originated with the third uplift. The Exostoma group (Exostoma, Pseudexostoma, and Oreoglanis) originated after the outline of the Qinghai/Tibet Plateau was formed. The speciation of this group was not strong and the distribution limited.
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For others, the BSC is the preferred definition of species. Many geneticists who work on speciation prefer the BSC because it emphasizes the role of reproductive isolation. It has been argued that the BSC is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection.Hopf, F.A.; Hopf, F.W. (1985).
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The first known instance of hybrid speciation in marine mammals was discovered in 2014. The clymene dolphin (Stenella clymene) is a hybrid of two Atlantic species, the spinner and striped dolphins. In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the beluga whale and narwhal; dubbed the narluga.
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The evolutionary biologist James Mallet maintains that the mantra repeated concerning Darwin's Origin of Species book having never actually discussed speciation is specious. The claim began with Thomas Henry Huxley and George Romanes (contemporaries of Darwin's), who declared that Darwin failed to explain the origins of inviability and sterility in hybrids.Mallet, James (2013). Darwin and species.
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Population genetics is the branch of biology that provides the mathematical structure for the study of the process of microevolution. Ecological genetics concerns itself with observing microevolution in the wild. Typically, observable instances of evolution are examples of microevolution; for example, bacterial strains that have antibiotic resistance. Microevolution may lead to speciation, which provides the raw material for macroevolution.
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These cycles would have caused fluctuation in the diversity and extent of rainforests. If this was the case, the current diversity of the Amazon rainforest would be a recent speciation in a changing environment. However, the floral record from the Cerrejón Formation shows that the current diversity of the Amazon Rainforest can be traced back into the early Cenozoic.
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Seriola dorsalis, the California yellowtail is a species of ray-finned fish of the family Carangidae.Martinez-Takeshita, N., D. M. Purcell, C. L. Chabot, M. T. Craig, C. N. Paterson, J. R. Hyde, & L. G. Allen. 2015. A tale of three tails: cryptic speciation in a globally distributed marine fish of the genus Seriola. Copeia, 103(2): 357-368.
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Each group member is found in hot, arid regions with low rainfall. They prefer soil that is loose, gravelly, and well-drained. C. cylindrata is found only in the middle portion of Baja California, mostly in Baja California Sur. Botanists Bemis and Whitaker suggest that C. cordata and C. cylindrata may be a case of sympatric speciation.
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Due to its wide spread habitat, Hemitrichia serpula has been used to study the process of speciation and gene flow in the Myxomycetes. Many species of slime molds can be found in lowland forests of most of the major continents, including Asia, Europe, North America and South America, demonstrating their ability to disperse spores upwards of thousands of miles.
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The hierarchy of biological classification's eight major taxonomic ranks. Intermediate minor rankings are not shown. This diagram uses a 3 Domains / 6 Kingdoms format Multiple speciation events create a tree structured system of relationships between species. The role of systematics is to study these relationships and thus the differences and similarities between species and groups of species.
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This has been rectified by moving some species (Gastrophryne usta and Gastrophryne pictiventris) to Hypopachus. Gastrophryne frogs were the first species to be recognized to be experiencing speciation by reinforcement and lead to the coining of the term reinforcement by W. Frank Blair in 1955;Sætre, Glenn- Peter. (2012). Reinforcement. eLS. a concept proposed by Theodosius Dobzhansky decades earlier.
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Speciation within the genus can be difficult to confirm, partly due to hybridisation, which is at least known to occur between Diadema savignyi and Diadema setosum. The species vary in types of sea bed they inhabit, with Diadema savignyi inhabiting sandy beds and back reef where damaged; while Diadema setosum can also commonly be found among seagrass.
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Moreover, another genetic group was created: coastal species. However, no evidence were shown for more environment implication in driving speciation, which may be the result of both adaptation and allopatry. The concept of cryptic species, rare among such an iconic group, is mentioned, regarding several divergent populations. In the meantime, Escapa and Catalano published a phylogenetic analysis using parsimony.
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The Genovesa ground finch (Geospiza acutirostris) is a small bird native to the Galápagos Islands. It was considered a subspecies of the sharp-beaked ground finch (Geospiza difficilis) endemic to Genovesa Islands.Grant, Peter R.; Grant, B. Rosemary & Petren, Kenneth (2000). The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands. Biol.
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Oxaloacetate produces oxalate by hydrolysis.Gadd, Geoffrey M. "Fungal production of citric and oxalic acid: importance in metal speciation, physiology and biogeochemical processes" Advances in Microbial Physiology (1999), 41, 47-92. :oxaloacetate + H2O oxalate + acetate This process is catalyzed by the enzyme oxaloacetase. This enzyme is seen in plants, but is not known in the animal kingdom.
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These adaptations allow the butterflies to extract important amino acids from the pollen, which, in addition to general nutrition benefits, allows H. melpomene to have brighter colors and be more distasteful to predators than their non-pollen-foraging counterparts. It is thought that this foraging adaptation and subsequent enhancement of coloration contributed to the speciation of Heliconius.
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New York: W.H. Freeman. Barth, F.G. and A. Schmid, eds. (2001). Ecology of Sensing, Ch.1. Springer. This field covers topics ranging from the neurobiological mechanisms of sensory systems to the behavioral patterns employed in the acquisition of sensory information to the role of sensory ecology in larger evolutionary processes such as speciation and reproductive isolation.
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The authors concluded that speciation must have occurred and that the two new species were ancestral to the prior species. Just as in most of evolutionary biology, this example represents the interdisciplinary nature of the field and the necessary collection of data from various fields (e.g. oceanography, paleontology) and the integration of mathematical analysis (e.g. biometry).
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Genetic studies suggest that the Cephalorhynchus dolphins originated from a single common ancestor in South Africa, from which Heaviside's is the basal species. Radiation around the southern hemisphere following the Antarctic Circumpolar Current (otherwise known as the West Wind Drift), first to New Zealand and then to South America, led to the subsequent speciation within the genus.
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The two species of Drepanornis as well as the two species of Epimachus separated about 10 and 7 mya, respectively. While the two species of Drepanornis occupy different elevations in low- and mid-montane forests, the two species of Epimachus are altitudinal replacements in mountain forests; these two cases could represent old cases of altitudinal speciation.
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In other cases, they can help us understand how important patterns of behaviour were able to arise – on the back of a simple gene mutation. Finally, they can help provide key insight on the nature of speciation events which can occur when a behaviour mutation changes the courtship methods and manner of mating in sexually reproducing species.
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Satellite picture of Csepel Island within Budapest Csepel Island (Hungarian: Csepel-sziget, ) is the largest island on the Danube in Hungary. It is long; its width after sections of bifurcation and rejoining (confluence) varies from . It has an area of and its population is 165,000.Speciation of beryllium, nickel, and vanadium in soil samples from Csepel Island, Hungary.
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Hybrid zones can be either primary or secondary. Primary hybrid zones occur where divergence is taking place between adjacent populations of a previously homogeneous species, possibly leading to parapatric speciation. As a population spreads across a contiguous area it may spread into an abruptly different environment. Through adaptation to the new environment, the adjacent populations begin parapatric divergence.
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Reproductive isolation is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model. A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form, without increasing the number of resultant species.
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Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422. The pungu is threatened because of pollution and sedimentation from human activities. Konia, Myaka and Stomatepia are three other equally threatened genera of cichlids that also are endemic to Lake Barombi Mbo.
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Richerson, J.V., Borden, J.H., Hollingdale, J. (1972). Morphology of a unique sensillum placodeum on the antennae of Coiliodes brunneri (Hymenoptera:Braconidae). Canadian Journal of Zoology. 50(7):909-913. With respect to the sensillum, if there is a different morphology, then it is likely that these two or more species are different from one another based on phylogenetic speciation.
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It reaches up to in standard length. Unusually, the yellow swordtail appears to be the result of hybrid speciation, and its ancestors a platy species and a swordtail species. The southern mountain swordtail (X. monticolus), which is found further south in the Coatzacoalcos River basin than the yellow swordtail, is the result of a similar event.
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Some recent studies have documented exceptionally low rates of ecological and phenotypic evolution despite rapid speciation. This has been termed a "non-adaptive radiation" referring to diversification not accompanied by adaptation into various significantly different niches. Such radiations are explanation for groups that are morphologically conservative. Persistent adaptation within an adaptive zone is a common explanation for morphological stasis.
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Rock lizards of the Caucasus: systematics, ecology and phylogenesis of the polymorphic groups of Caucasian rock lizards of the subgenus Archaeolacerta. Nauka: Leningrad [in Russian: English translation published by the Indian National Scientific Documentation Centre, New Delhi, 1978].Tarkhnishvili DN (2012) Evolutionary History, Habitats, Diversification, and Speciation in Caucasian Rock Lizards. In: Advances in Zoology Research, Volume 2 (ed.
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"Gould, S. J. 2002. The Structure of Evolutionary Theory. Cambridge MA: Harvard University Press, p. 872. Philosopher Kim Sterelny in clarifying the meaning of stasis adds, "In claiming that species typically undergo no further evolutionary change once speciation is complete, they are not claiming that there is no change at all between one generation and the next.
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Like Darwin, Romanes's theories were met with scepticism and were not accepted initially. The majority of Romanes's work attempted to make a connection between animal consciousness and human consciousness. Some problems were encountered during his research that he addressed with the development of physiological selection. This was Romanes's answer to three objections to Darwin's isolation theory of speciation.
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Pantala flavescens is considered as a global panmictic population. A panmictic population of Monostroma latissimum, a marine green algae, shows sympatric speciation in southwest Japanese islands. Although panmictic, the population is diversifying. Dawson's Burrowing bee, Amegilla dawsoni, may be forced to aggregate in common mating areas due to uneven resource distribution in its harsh desert environment.
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Mycocepurus goeldii is a species of ant in the genus Mycocepurus. The species is parasitised by a closely related species, Mycocepurus castrator. The two diverged recently, around 37,000 years ago, and evolved in the same geographic region, making the parasite–host pair an example of sympatric speciation. M. castrator is directly descended from M. goeldii, its host.
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Such relationships are not uncommon among social parasites, as recognized by Emery's rule. Less common are cases like M. castrator's, where two species diverge without the benefit of geographic isolation, known as sympatric speciation. Rabeling et al. (2014) analyzed divergence of mitochondrial versus nuclear DNA, finding that the nuclear alleles bore more similarities than the mitochondrial alleles.
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Orator Fuller Cook Jr. (May 28, 1867 – April 23, 1949) was an American botanist, entomologist, and agronomist, known for his work on cotton and rubber cultivation and for coining the term "speciation" to describe the process by which new species arise from existing ones. He published nearly 400 articles on topics such as genetics, evolution, sociology, geography, and anthropology.
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Konia is a small genus of critically endangered cichlids endemic to Lake Barombi Mbo in western Cameroon. Although generally recognized as distinct, the genus is very close to Sarotherodon.Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation.
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Various alternative explanations for the patterns observed in nature have been proposed. There is no single, overarching signature of reinforcement; however, there are two proposed possibilities: that of sex asymmetry (where females in sympatric populations are forced to become choosy in the face of two differing males)L. Partridge and G. A. Parker. (1999). Sexual conflict and speciation.
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The earliest fossils of the antilopines are from the middle Miocene, though studies show the existence of the subfamily from the early Miocene. Speciation occurred in the tribe Antilopini during the middle or upper Miocene, mainly in Eurasia. Tribe Neotragini seems to have appeared in Africa by the end of Miocene, and had become widespread by the Pliocene.
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This synchrony is essential so that male and female gametes can meet. Corals must rely on environmental cues, varying from species to species, to determine the proper time to release gametes into the water. The cues involve lunar changes, sunset time, and possibly chemical signalling. Synchronous spawning may form hybrids and is perhaps involved in coral speciation.
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Sexual dimorphism can be viewed as something that can accelerate the rate of speciation. In non- predatory birds, males are typically larger than females. However, in birds of prey, the opposite is the case. For instance, the kestrel is a type of falcon in which males are the primary providers, and the females are responsible for nurturing the young.
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Maize growth improved after an amendment of arbuscular mycorrhizae and biochar. This amendment can also decrease cadmium uptake by crops.Liu, L., Li, J., Yue, F., Yan, X., Wang, F., Bloszies, S. and Wang, Y. (2018). Effects of arbuscular mycorrhizal inoculation and biochar amendment on maize growth, cadmium uptake and soil cadmium speciation in Cd-contaminated soil.
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Although bats evolved in the Palearctic, their origins antedate that of the lyassaviruses by millions of years, which argues against their co-speciation. The evolution rate in the N gene in the Africa 2 lineage has been estimated to be 3.75×10−3 substitutions per site per year. This rate is similar to that of other RNA viruses.
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"On the Complexity of the Saccharomyces bayanus Taxon: Hybridization and Potential Hybrid Speciation." PLoS ONE 9.4 (2014): e93729. Most commonly strain CBS 380 (Saccharomyces bayanus) has been attributed as the second parent, but it has also been conclusively demonstrated as possessing a hybrid genotype of its own.Vaughan-Martini A, Martini A (2011) Chapter 61 - Saccharomyces Meyen ex Reess (1870).
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Most species are endemic small areas, many of which are small islands that emerged from the ocean floor in recent geological times with no connection to the mainland. These were likely inhabited by pregnant females surviving in floating logs, while most of the other speciation is believed to have occurred due to fragmentation of the former supercontinent Gondwana.
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The initial split into multiple species within this genus is based on a review from 1999 where it, based on the phylogenetic species concept, was argued that all then recognized taxa should be considered monotypic species.Beresford, P. & Cracraft, J. (1999). Speciation in African forest robins (Stiphrornis): species limits, phylogenetic relationships, and molecular biogeography. American Museum Novitates 3270: 1–22.
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Axel Meyer (born August 4, 1960) is an evolutionary biologist and a professor of zoology and evolutionary biology at the Universität Konstanz, Germany. Meyer is best known for his work on the evolution and adaptive radiation of African cichlid fishes, fish-specific genome duplications, molecular phylogenetics of vertebrates, and the role of ecological and sexual selection in speciation.
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This active rift zone creates lakes that are extremely deep and difficult to naturally fill with sediment. Due to the prolonged life of ancient lakes, they serve as models for isolated evolutionary traits and speciation. Most of the world's bodies of water are less than 18,000 years old. There are only 20 ancient lakes over 1 million years old.
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There is substantial morphological variability evident in O. n. nigriplantare, and a shallow level of genetic differential between islands within the Chatham Islands indicating low gene flow between islands, but not speciation between islands. The level of genetic and morphological divergence between O. n. nigriplantare and Oligosoma nigriplantare polychroma might warrant their recognition as distinct species.
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Drosophila species on the Hawaiian archipelago have helped researchers understand speciation processes in great detail. It is well established that Drosophila has undergone an adaptive radiation into hundreds of endemic species on the Hawaiian island chain; originating from a single common ancestor (supported from molecular analysis).DeSalle R. (1995). Molecular approaches to biogeographic analysis of Hawaiian Drosophilidae.
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Methods used to estimate the evolutionary divergence of taxa, including the multispecies coalescent process, suggest that most diversification of Melanohalea occurred throughout the Miocene (23.03 to 5.333 BP) and Pliocene (5.333 million to 2.58 BP), and divergence estimates suggest that diversification that occurred during the glacial cycles of the Pleistocene was not accompanied by speciation in Melanohalea.
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Tanja Stadler studied Applied Mathematics at the Technical University of Munich, the University of Cardiff, and the University of Canterbury. She obtained a Master degree in 2006 and a PhD in 2008 from the Technical University of Munich on 'Evolving Trees – Models for Speciation and Extinction in Phylogenetics' (with Prof. Anusch Taraz and Prof. Mike Steel).
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From the point of view of taxonomy, hybrids differ according to their parentage. Hybrids between different subspecies (such as between the Dog and Eurasian wolf) are called intra-specific hybrids. Interspecific hybrids are the offspring from interspecies mating; these sometimes result in hybrid speciation. Intergeneric hybrids result from matings between different genera, such as between sheep and goats.
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Model of the phylogeny of Hominini over the past 10 million years. Both Sahelanthropus and Orrorin existed during the estimated duration of the ancestral chimpanzee-human speciation events, within the range of eight to four million years ago (Mya). Very few fossil specimens have been found that can be considered directly ancestral to genus Pan. News of the first fossil chimpanzee, found in Kenya, was published in 2005. However, it is dated to very recent times—between 545 and 284 thousand years ago. The divergence of a "proto-human" or "pre-human" lineage separate from Pan appears to have been a process of complex speciation-hybridization rather than a clean split, taking place over the period of anywhere between 13 Mya (close to the age of the tribe Hominini itself) and some 4 Mya.
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The botanist Verne Grant proposed the term quantum speciation that combined the ideas of J. T. Gulick (his observation of the variation of species in semi-isolation), Sewall Wright (his models of genetic drift), Mayr (both his peripatric and genetic revolution models), and George Gaylord Simpson (his development of the idea of quantum evolution). Quantum speciation is a rapid process with large genotypic or phenotypic effects, whereby a new, cross-fertilizing plant species buds off from a larger population as a semi- isolated peripheral population. Interbreeding and genetic drift takes place due to the reduced population size, driving changes to the genome that would most likely result in extinction (due to low adaptive value). In rare instances, chromosomal traits with adaptive value may arise, resulting in the origin of a new, derivative species.
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This hypothesis of lineage diversification, however, can be unconvincing due to a lack of support for rapid speciation early in cetacean history. A second, more abiotic drive is better supported. Physical restructuring of the oceans has played a role in echolocation radiation. This was a result of global climate change at the Eocene-Oligocene boundary; from a greenhouse to an icehouse world.
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An OR gene radiation co-existed during the time of reptile dominance approximately 200 million years ago. This occurrence would have likely signaled a major speciation event or adaptive shift in the prevalent organisms. The earliest tetrapods thrived in aquatic environments prior to making their initial transition to land. Correspondingly, modern amphibians too began in water before emerging on land as adults.
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Oryzorictes hova eats insects like worms, and they spend some of their time above ground but mostly stay underground. They can also be found in rice fields. Not much is known about their mating or reproduction, but the most offspring they have is 4. Due to allopatric speciation, the rice tenrec has been separated into 3 distinct populations across Madagascar.
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Burns, J. 2000. A striking new species of skipper butterfly on the North Carolina coast. 51st Annual Meeting of the Lepidopterists Society, Wake Forest University, Winston-Salem, NC. Burns, J. 2015. Speciation in an insular sand dune habitat: Atrytonopsis (Hesperiidae: Hesperiinae) - mainly from the southwestern United States and Mexico - off the Carolina coast. Journal of the Lepidopterists' Society 69(4):275-292.
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Luis Fernando De León has published over 40 peer-reviewed scientific papers which together have received over 700 citations . His research focuses on adaptive divergence and speciation, human impacts on evolution, eco-evolutionary dynamics. His lab works primarily on Darwin's finches and weakly-electric fishes in the order Gymnotiformes. He was invited to be the Saul Speaker at Middlebury College in 2020.
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Tracing the evolution of these species has been problematic given the scarcity of good fossils. DNA sequences have become the preferred approach to understanding speciation. The order appears to have originated about 420 million years ago during the Silurian. The 39 extant species fall into three families—the Callorhinchids, Rhinochimaerids and Chimaerids with the callorhinchids being the most basal clade.
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It is thought that A. ocellaris specialized after diverging from the genus Premnas, and scientific evidence confirms that all clownfish belonging to the genus Amphiprion initially could withstand the stings of only one type of anemone; after further speciation the 28 different species of clownfish including A. ocellaris have specialized to be able to resist the poisonous stings of many different anemone species.
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Gage, M. J. G., Parker, G. a, Nylin, S. & Wiklund, C. Sexual selection and speciation in mammals, butterflies and spiders. Proceedings: Biological Sciences 269, 2309–16 (2002). Because of this, there are generally more males available to mate at a given time, making females a limited resource. This leads males to evolve aggressive mating behaviors which can help them acquire mates.
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In 2007, some analyses found that different call types were genetically different including the South Hills crossbill (call type 9). Furthermore, evidence suggested that the South Hills crossbill was in a coevolutionary arms race with the lodgepole pine, further leading to habitat isolation. In 2016, it was identified as phylogenetically distinct from the other call types. This is an example of sympatric speciation.
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The diverse speciation of chameleons has been theorized to have directly reflected the increase in open habitats (savannah, grassland, and heathland) that accompanied the Oligocene period. Monophyly of the family is supported by several studies. Daza et al. (2016) described a small (10,6 mm in snout-vent length), probably neonatal lizard preserved in the Cretaceous (Albian-Cenomanian boundary) amber from Myanmar.
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Also, the male sex determination gene in the hybrids is only found in the genome of the pool frog, further undermining stability.Guldager Christiansen, D. (2010): Genetic Structure and Dynamics of All-hybrid Edible Frog Populations. Doctoral dissertation for the University of Zurich. 140 pages Such instability can also lead to rapid reduction of chromosome numbers, creating reproductive barriers and thus allowing speciation.
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Later he focused on the speciation of birds in inland Australia, making several expeditions in the course of his research. He also discovered that the wedgebill comprised two separate species, the chirruping and chiming wedgebills. He was a member of the Royal Australasian Ornithologists Union (RAOU) and served on its Taxonomic Advisory Committee. He also contributed numerous papers to its journal, the Emu.
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It is assumed that the normal activity of these speciation genes is to "inhibit" the expression of the genes that allow the growth of the hybrid. There will also be regulator genes. A number of these genes have been found in the melanogaster species group. The first to be discovered was "Lhr" (Lethal hybrid rescue) located in Chromosome II of D. simulans.
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The resulting founder effect and either non-existent or inferior competition resulted in speciation as the lemur ancestors radiated out to fill open or insufficiently guarded niches. Today, the endemic primate fauna of Madagascar contains over three-quarters of the extant species of the suborder Strepsirrhini, which had been abundant throughout Laurasia and Africa during the Paleocene and Eocene epochs.
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He also helped the university to form a department Library for Biology students. In 1928 Patterson was designated Director of Research in Zoology at the university. When Muller managed to prove that X rays prove mutations in Drosophilia, Patterson shifted his focus towards the field of genetics and speciation. Patterson used the X rays on larvae to prove that embryos mutate following irradiation.
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There are, however, problems with this proposal of cryptic speciation (cryptic species). The basis of these data from one mitochondrial gene. mtDNA data are, however, only one source of information about the status of taxa and the use of one mtDNA gene as a sole criterion for species identification is disputed. The allozyme data should also be taken into account.
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PMID 18558658 Silene flowers are frequently visited by flies, such as Rhingia campestris. Silene species have also been used to study speciation, host-pathogen interactions, biological species invasions, adaptation to heavy-metal-contaminated soils, metapopulation genetics, and organelle genome evolution. Notably, some members of the genus Silene hold the distinction of harboring the largest mitochondrial genomes ever identified.Sloan DB et al. 2012.
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6: 146-151. One view maintains that male ornaments co-evolve with female preferences. The selection of an ornamented mate causes genes that influence expression of the selected male trait and genes coding for female preference for this trait to be passed on to offspring.Lande, R. (1981). “Models of speciation by sexual selection on polygenic traits.” Proc. Natn. Acad. Sci.
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Quaternary Science Reviews Volume 27, Issues 9-10, May 2008, Pages 1024-1046 Naomi Porat and Greg Botha The geological history of the region suggests that the current ecosystems here may be of recent derivation and many endemic plant taxa comply with the concept of neo- endemics (recent locally evolved species), and biological evolution (notably speciation) is still in an active phase.
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He has pioneered experiments into disruptive selection (selection in the same population for both extremes and against intermediates), and (again contrary to theoretical expectation), showed such selection could be extremely effective, increasing variance, establishing and maintaining polymorphisms, and, if the selected individuals were allowed to choose their mates, dividing the population into two partially isolated parts, something which is a step towards speciation.
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Natural selection in an environment produces reproductive success, which benefits the species. Speciation is a process of evolution through which new biological species are formed. Dobzhansky studied the specifics of sexual, physiological, and behavioral isolating mechanisms in Drosophila pseudoobscura and Drosophila paulistrorum. Like many of his other studies, Dobzhansky's work on reproductive isolation was aimed at studying the process of evolution in action.
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Genetics and the Origin of Species has two main points to make. The first is that speciation is a genuine problem that must be explained by the theory of evolution. In nature, there is not a single population of organisms separated from each other by small variations. Instead, the natural world is divided into species, each with its own limited range of variability.
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An isolating mechanism prevents members of two different species from successfully producing offspring. Dobzhansky invented the term, and in the eighth chapter he discusses their role in speciation. His views were sufficiently original for him to publish them in a journal article as well. Although previous authors had recognized the importance of isolation, their reasons were entirely different from his.
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The current hawthorn feeding population does not normally feed on apples. Some evidence, such as the fact that six out of thirteen allozyme loci are different, that hawthorn flies mature later in the season and take longer to mature than apple flies; and that there is little evidence of interbreeding (researchers have documented a 4–6% hybridization rate) suggests that speciation is occurring.
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An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment, they are termed adaptive radiations.
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The species has purple skin and blue eyes and lives underground. It differs genetically, morphologically, and acoustically from the closely related Nasikabatrachus sahyadrensis. Speciation between the two species is likely caused by the different monsoon seasons on the different sides of the Western Ghats, causing N. sahyadrensis to breed between May and August and N. bhupathi to breed between October and December.
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Rhagoletis juglandis, also known as the walnut husk fly, is a species of tephritid or fruit fly in the family Tephritidae. It is closely related to the walnut husk maggot Rhagoletis suavis (Loew, 1862). This species of fly belongs to the R. suavis group, which has a natural history consistent with allopatric speciation. The flies belonging to this group are morphologically distinguishable.
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Beilschmiedia falls within the Lauraceae, a family of aromatic evergreen trees or shrubs. Many botanical species are similar in foliage to the Lauraceae due to convergent evolution. Those plants are adapted to high rainfall and humidity. The patterns of speciation in the Lauraceae indicate, since the onset of aridification on the continents 15 million years ago (Mya), rainforest species diversified.
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The A. pisum and Buchnera endosymbiotic relationship is likely to have evolved 160-280 million years ago. Phylogenetic analysis shows that Buchnera is a monophyletic group and that the phylogenies of Buchnera and A. pisum coincide. Therefore, there was likely one original Buchnera infection of the common ancestor of aphids and co-speciation of the holosymbiont has occurred since then.oran, N.A., et al.
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They depict relations among individuals that can speciate and diverge from one another. The evolutionary process of speciation creates groups that are linked by a common ancestor and all its descendants. Species inherit traits, which are then passed on to descendants. Evolutionary biologists use systematic methods and test phylogenetic theory to observe and explain changes in and among species over time.
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The N. coriiceps genome was sequenced in 2014. Results indicated rapid evolution of genes during speciation, especially in proteins that code for mitochondrial proteins and hemoglobin. In addition, the authors found that many N. coriiceps genes are reflective of adaptation to cold temperatures, with specialized genes related to the species' modified heat shock response as well as enhanced oxidative phosphorylation at cold temperatures.
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However, this finding rests heavily on the fact that active and passive dispersers have been grouped together in the analyses. When the same data are separated into two categories (active and passive dispersers) a pattern emerges. Jenkins and others (2007) have found that for active dispersers larger organisms will disperse greater distances. Regardless of this correlation its effects on speciation rates remain unclear.
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Extensive exploration in the range of the genus in the Western Ghats of India suggests an under- estimation of the number of species in the genus. A study of the diverse specie of the genus show that the separate isolated massifs of the Western Ghats played a major role in the speciation and habitat specificity seen in the genus of bush frogs.
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"Towards a New Evolutionary Theory". Interciencia 35: 862-868. at a chromosomal level, meiotic recombination causes evolution to be reticulate; at a species level, reticulation arises through hybrid speciation and horizontal gene transfer; and at a population level, sexual recombination causes reticulation. The adjective reticulate stems from the Latin words reticulatus, "having a net- like pattern" from reticulum, "little net.""reticulate".
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Colored lines indicate distributions, whether allopatric or sympatric. Patterns of increased endemism at higher elevations on both islands and continents have been documented on a global level. As topographical elevation increases, species become isolated from one another; often constricted to graded zones. This isolation on "mountain top islands" creates barriers to gene flow, encouraging allopatric speciation, and generating the formation of endemic species.
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A growing trend in the world of elemental analysis has revolved around the speciation, or determination of oxidation state of certain metals such as chromium and arsenic. One of the primary techniques to achieve this is to separate the chemical species with high-performance liquid chromatography (HPLC) or field flow fractionation (FFF) and then measure the concentrations with ICP-MS.
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Beginning in 1983, some field guides for birds use sonograms to document the calls and songs of birds. The sonogram is objective, unlike descriptive phrases, but proper interpretation requires experience. Sonograms can also be roughly converted back into sound. Bird song is an integral part of bird courtship and is a pre-zygotic isolation mechanism involved in the process of speciation.
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The theory is based on significant climatic changes occurring in and around the equator during the Quaternary period. During these climatic changes of glaciation, the northern rainforests of South America received less rainfall and deteriorated, then subsequently expanded during interglaciation. This change caused allopatric speciation to occur among many species and gave rise to a new subspecies - P. p. melanonota.Ernst, CH. 1983.
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University of California, Berkeley Species within the genus likely adapted to riparian habitats prior to the Andean uplift in the Cretaceous and Early Tertiary. As Andean uplift occurred, creating a more montane environment, it lifted the species and speciation resulted for the medium- to higher-altitude species members including A. coynei; this higher- altitude adaptation likely reflected the ensuing vegetation and climate.
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Inorganic mercury Hg2+ and methyl mercury has the ability to get adsorbed in to particles. A positive correlation of binding is observed for the amount of organic matter vs. the concentration of these mercury species showing that most of them bind to organic matter.13\. Boszke, L.; Glosinska, G.; Siepak, J.; Some aspects of speciation of mercury in a water environment. Pol.
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PR domainpositive-regulatory domain zinc finger protein 9 is a protein that in humans is encoded by the PRDM9 gene. PRDM9 is responsible for positioning recombination hotspots during meiosis by binding a DNA sequence motif encoded in its zinc finger domain. PRDM9 is the only speciation gene found so far in mammals, and is one of the fastest evolving genes in the genome.
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Accordingly, the genome stasis hypothesis is challenged by the recent finding that the genome of the two extant coelacanth species L. chalumnae and L. menadoensis contain multiple species-specific insertions, indicating transposable element recent activity and contribution to post-speciation genome divergence. Such studies, however, challenge only a genome stasis hypothesis, not the hypothesis of exceptionally low rates of phenotypic evolution.
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The effects of Wolbachia in Trichogramma have several evolutionary implications. Commonly, uninfected wasps are unable to breed with infected wasps. Many generations of reproductive isolation of these different groups may result in speciation. In addition, some hosts can evolve with a dependency on Wolbachia for core reproductive functions, such as oogenesis, so that eventually an infection is a requirement for successful reproduction.
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Morgan-Richard's research has focused on topics in evolutionary biology such as speciation and hybridisation, as well as conservation biology, using population genetics, and phylogenetic methods. Native New Zealand invertebrates including wētā, stick insects, and snails are often the subject of her research. She has scientifically described multiple species of wētā. Morgan-Richard's phylogenetic research has also focused on birds and their parasites.
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The sequential colonization and speciation of the Chasiempis sandwichensis subspecies (denoted by the orange arrows) with their divergence times and island geological ages. Uniquely among Hawaiian passerines, the distribution of the elepaio is peculiarly discontinuous. According to fossil remains, the birds did not occur on Maui Nui or its successor islands. Their current distribution is absent from the Maui Nui island group.
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Possibly, G. filiasaulae has evolved without ever having been fully separated from its ancestor, a process known as speciation-with-gene-flow.Schilthuizen M., Rutten E. J. M. & Haase M. (2012). "Small-scale genetic structuring in a tropical cave snail and admixture with its above-ground sister species". Biological Journal of the Linnean Society 105: 727-740. doi:10.1111/j.1095-8312.2011.01835.
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Reinforcement's ubiquity is unknown, but the patterns of reproductive character displacement are found across numerous taxa and is considered to be a common occurrence in nature. Studies of reinforcement in nature often prove difficult, as alternative explanations for the detected patterns can be asserted. Nevertheless, empirical evidence exists for reinforcement occurring across various taxa and its role in precipitating speciation is conclusive.
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When a species is introduced into a new environment, it causes episodic selection. The invading species is exposed to other resident taxa, and hybridization may occur to produce a new species. If these hybrids are successful, they may outcompete their parent species.Brasier, C., Episodic Selection as a force in fungal microevolution, with special reference to clonal speciation and hybrid introgression.
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Climate change has a significant direct effect on terrestrial animals, by being a major driver of the processes of speciation and extinction. The best known example of this is the Carboniferous rainforest collapse, which occurred 350 million years ago. This event decimated amphibian populations and spurred on the evolution of reptiles. In general, climate change affects animals and birdlife in various different ways.
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The Wilson Bulletin, 105:688-691. In the 1960s, 17 individual birds were caught and measured and it was noted that the species wing length could range from 358 to 403 mm, giving them a medium-sized wing for a caracara, but a comparatively short tail.Vuilleumier, F. (1970) Generic relations and speciation patterns in the Caracaras (Aves: Falconidae). Breviora, 355:1-29.
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Genetic structure of Cenococcum geophilum populations in primary successional volcanic deserts on Mount Fuji as revealed by microsatellite markers. New Phytologist, 165(1), 285-293. Douhan & Rizzo (2005) found phylogenetically distinct lineages of C. geophilum at the scale of the soil sample supporting the hypothesis that there is cryptic sympatric speciation occurring in C. geophilum.Douhan, G. W., & Rizzo, D. M. (2005).
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S. mekongi appears to have invaded South East Asia in the mid-Pleistocene. Estimated speciation dates for the japonicum group: ~3.8 million years ago for S. japonicum/South East Asian schistosoma and ~2.5 million years ago for S. malayensis/S. mekongi. Schistosoma turkestanicum is found infecting red deer in Hungary. These strains appear to have diverged from those found in China and Iran.
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The breaking up of Gondwanaland led to large-scale speciation of Podocarpaceae. Until 1970, only seven Podocarpaceae genera were recognized: Podocarpus, Dacrydium, Phyllocladus, Acmopyle, Microcachrys, Saxegothaea, and Pherosphaera. All four of the African species fell under Podocarpus – P. falcatus, P. elongatus, P. henkelii, and P. latifolius. Taxonomists divided Podocarpus species into eight species groups based on leaf anatomy: Afrocarpus J.Buchholz & N.E.Gray, Dacrycarpus Endl.
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Erebia callias has been lumped with the Siberian brassy ringlets as they are almost alike morphologically. Though one might suspect stronger differentiation and perhaps marked cryptic speciation across the wide range, the Rocky Mountains population is apparently a very recent isolate. Its ancestors apparently crossed over the Bering Strait at the end of the Wisconsinian glaciation, about 15,000 to 10,000 years ago.
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Because of the large size and potentially greater genetic variation within the central population, mutations arise more readily. These mutations are left in the isolated peripheral populations, whereby, promoting reproductive isolation. Consequently, Brown suggested that during another expansion phase, the central population would overwhelm the peripheral populations, hindering speciation. However, if the species finds a specialized ecological niche, the two may coexist.
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Females tend to stay in their natal plants and prefer to mate and lay their eggs on it, which is called philopatry.Stearns, F. W., Tilmon, K. J., & Wood, T. K. (2013). Felsenstein’s “one-allele model” of speciation: The role of philopatry in the initial stages of host plant mediated reproductive isolation in Enchenopa binotata. Current Zoology, 59(5), 658-666.
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Generally, ferric sulfate is used as a solution generated from iron wastes. The actual speciation is vague but its applications do not demand high purity materials. Iron(III) sulfate is often generated as a solution rather than being isolated as a solid. It is produced on a large scale by treating sulfuric acid, a hot solution of ferrous sulfate, and an oxidizing agent.
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Mercury deposits in California are located mainly along the San Andreas Fault.Kim, C.S., Brown Jr., G.E., and Rytuba, J.J. (2000) Characterization and speciation of mercury- bearing mine wastes using X-ray absorption spectroscopy. The Science of the Total Environment, 261, 157-168. The deposits are related to the transition of the North American plate and the Pacific plate boundary from converging to transform.
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Drosophila orientacea is a member of the Testacea species group of Drosophila. Testacea species are specialist fruit flies that breed on the fruiting bodies of mushrooms. Drosophila orientacea is found in northern Japan on the island of Hokkaido. However, the European species Drosophila testacea and D. orientacea can produce viable hybrids, blurring the level of speciation between the two species.
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Maintained gene flow between two populations can also lead to a combination of the two gene pools, reducing the genetic variation between the two groups. It is for this reason that gene flow strongly acts against speciation, by recombining the gene pools of the groups, and thus, repairing the developing differences in genetic variation that would have led to full speciation and creation of daughter species. For example, if a species of grass grows on both sides of a highway, pollen is likely to be transported from one side to the other and vice versa. If this pollen is able to fertilise the plant where it ends up and produce viable offspring, then the alleles in the pollen have effectively been able to move from the population on one side of the highway to the other.
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The Dobzhansky–Muller model proposes that reproductive incompatibilities between species are caused by the interaction of the genes of the respective species. It has been demonstrated recently that Lhr has functionally diverged in D. simulans and will interact with Hmr which, in turn, has functionally diverged in D. melanogaster to cause the lethality of the male hybrids. Lhr is located in a heterochromatic region of the genome and its sequence has diverged between these two species in a manner consistent with the mechanisms of positive selection. An important unanswered question is whether the genes detected correspond to old genes that initiated the speciation favoring hybrid non-viability, or are modern genes that have appeared post-speciation by mutation, that are not shared by the different populations and that suppress the effect of the primitive non- viability genes.
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Ensatina eschscholtzii has been described as a ring species in the mountains surrounding the Californian Central Valley.Wake, D. (1997) Incipient species formation in salamanders of the Ensatina complex Proceedings of the National Academy of Sciences USA 94:7761-7767 The complex forms a horseshoe shape around the mountains, and though interbreeding can happen between each of the 19 populations around the horseshoe, the Ensatina eschscholtzii subspecies on the western end of the horseshoe cannot interbreed with the Ensatina klauberi on the eastern end.Dawkins, R. (2004) The Ancestor's Tale: A Pilgrimage to the Dawn of Life , Ring Species (The Salamander's Tale) As such, it is thought to be an example of incipient speciation, and provides an illustration of "nearly all stages in a speciation process" (Dobzhansky, 1958).Dobzhansky T. (1958) in A Century of Darwin, ed Barnett S A (Harvard Univ.
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Reproductive isolation acts as the primary mechanism driving genetic divergence in allopatry and can be amplified by divergent selection. Pre-zygotic and post-zygotic isolation are often the most cited mechanisms for allopatric speciation, and as such, it is difficult to determine which form evolved first in an allopatric speciation event. Pre- zygotic simply implies the presence of a barrier prior to any act of fertilization (such as an environmental barrier dividing two populations), while post-zygotic implies the prevention of successful inter-population crossing after fertilization (such as the production of an infertile hybrid). Since species pairs who diverged in allopatry often exhibit pre- and post- zygotic isolation mechanisms, investigation of the earliest stages in the life cycle of the species can indicate whether or not divergence occurred due to a pre-zygotic or post-zygotic factor.
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Instead Darwin used the emergence of such features in breeding populations as evidence that mutation can occur at random within breeding populations, which is a central premise of his model of selection in nature. Later in his career, Castle would refine his model for speciation to allow for small variation to contribute to speciation over time. He also was able to demonstrate this point by selectively breeding laboratory populations of rats to obtain a hooded phenotype over several generations. Castle's was perhaps the first attempt made in the scientific literature to direct evolution by artificial selection of a trait with continuous underlying variation, however the practice had previously been widely employed in the development of agriculture to obtain livestock or plants with favorable features from populations that show quantitative variation in traits like body size or grain yield.
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However, mutationism did not entirely vanish. In 1940, Richard Goldschmidt again argued for single-step speciation by macromutation, describing the organisms thus produced as "hopeful monsters", earning widespread ridicule. In 1987, Masatoshi Nei argued controversially that evolution was often mutation- limited. Modern biologists such as Douglas J. Futuyma conclude that essentially all claims of evolution driven by large mutations can be explained by Darwinian evolution.
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Polyploid plants can arise spontaneously in nature by several mechanisms, including meiotic or mitotic failures, and fusion of unreduced (2n) gametes. Both autopolyploids (e.g. potato) and allopolyploids (such as canola, wheat and cotton) can be found among both wild and domesticated plant species. Most polyploids display novel variation or morphologies relative to their parental species, that may contribute to the processes of speciation and eco-niche exploitation.
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Synechococcus sp. PCC7942 has kaiA whereas P.marinus does not, even though they are closely related unicellular organisms, further demonstrating the evolutionary youth of the kaiA gene. KaiA genes are also found in the genomes of the species of the kaiC subtree, in younger clades than Prochlorococcus. Thus kaiA genes most likely arrived after the speciation of Synechococcus and Prochlorococcus, about 1,051 ± 1,16.9 and 944 ± 92.9 Mya.
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A river of genes may fork, mostly due to the geographical separation between two populations of organisms. Because genes in the two branches never share the same bodies, they may drift apart until genes from the two branches become incompatible. Organisms created by these two branches form separate, non- interbreeding species, completing the process of speciation. "Revolutionary Evolutionist", profile by Michael Schrage, Wired, July 1995.
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Two lineages from the European Crassulaceae eventually dispersed to North America and underwent subsequent diversification. The Aeonium clade dispersed from northern Africa to adjacent Macaronesia. Distinct centers of speciation developed in Macaronesia (Aeonium clade), Mexico (Sedum and Echeverioideae in clade 7), and southeastern Asia (Sedum sarmentosum, and S. morissonensis in Acre clade). On arrival in the Northern hemisphere the Sempervivoideae reached its greatest diversity.
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Two segments of DNA can have shared ancestry because of either a speciation event (orthologs) or a duplication event (paralogs). Homology among proteins or DNA is typically inferred from their sequence similarity. Significant similarity is strong evidence that two sequences are related by divergent evolution of a common ancestor. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous.
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Female choice is present in cichlids because the female does much of the work in raising the offspring, while the male has little energy input in the offspring. She exerts sensory bias when picking males by choosing those that have colors similar to her or those that are the most colorful. This helps maintain sympatric speciation within the lakes. Cichlids also use acoustic reproductive communication.
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Lepetodrilus is a genus of small, deep-sea sea snails, hydrothermal vent limpets, marine gastropod mollusks in the family Lepetodrilidae. A few species have been found in methane and sulfide seeps.Shannon B. Johnson, Curtis R. Young, William J. Jones, Anders Warén and Robert C. Vrijenhoek, Migration, Isolation, and Speciation of Hydrothermal Vent Limpets (Gastropoda; Lepetodrilidae) across the Blanco Transform Fault, Biological Bulletin, Vol. 210, No. 2 (Apr.
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A female in hand All taxa within the genus Stiphrornis were considered part of a single species, S. erythrothorax, until 1999, when it was argued, based on the phylogenetic species concept, that all then-recognized taxa should be considered monotypic species.Beresford, P. & Cracraft, J. (1999). Speciation in African forest robins (Stiphrornis): species limits, phylogenetic relationships, and molecular biogeography. American Museum Novitates 3270: 1–22.
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The long nectar spurs on this Aquilegia allow specialisation for a certain pollinator. A key innovation may result in reproductive isolation, whereby those individuals with the innovation no longer breed with those without. This can lead to rapid speciation as the two populations separate and accumulate mutations. The nectar spurs in Aquilegia, a diverse genus of flowering plant, are considered a key innovation because of this.
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This will lead to an influx of foreign genes into the parent population, a situation called an introgression. Introgression is a source of genetic variation, and can in itself facilitate speciation. There is evidence that introgression is a ubiquitous phenomenon in plants and animals, even in humans, where genetic material from Neanderthals and Denisovans is responsible for much of the immune genes in non-African populations.
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The largest specimen of Apateon and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae. Fossil Record.12(1):83-90. In the Late Carboniferous and Early Permian, western Europe was subjected to annual and long-lasting changes between dry and monsoon periods which produced highly variable lake environments and thus rapid diversification and speciation of amphibian populations.Ronchi, A. and Schneider, J.W. 2007.
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In organisms with sexual reproduction, incomplete lineage sorting may result in inconsistent phylogenetic trees, depending on which genes are assessed. It is also possible that multiple surviving lineages are generated while interbreeding is still significantly occurring (polytomy). Interbreeding is possible over periods of about 10 million years. Typically speciation occurs over only about 1 million years, which makes it less likely multiple long surviving lineages developed "simultaneously".
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The history of such attempts is described in Rice and Hostert (1993). Diane Dodd used a laboratory experiment to show how reproductive isolation can evolve in Drosophila pseudoobscura fruit flies after several generations by placing them in different media, starch- or maltose-based media. File:Drosophila speciation experiment.svg Dodd's experiment has been easy for many others to replicate, including with other kinds of fruit flies and foods.
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Clarkia lingulata is a rare species of wildflower known by the common name Merced clarkia. This plant is endemic to Mariposa County, California, where it is known from only two sites near the Merced River. It is thought to have evolved very rapidly, outside the usual model of allopatric speciation, from its parental species Clarkia biloba. It is a state-listed endangered species in California.
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Gascon, Claude; Malcolm, Jay R.; Patton, James L.; Bogart, James P. "Riverine barriers and the geographic distributions of Amazonian species." Proceedings of the National Academy of Sciences of the United States of America 97.25 (2000): 13672-3677. These results indirectly dispute the aspects of the hypothesis that insist on speciation caused by riverine barriers. The validity of the hypothesis was tested further by examining poison dart frogs.
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The Hominini, or hominins, form a taxonomic tribe of the subfamily Homininae ("hominines"). Hominini includes the extant genera Homo (humans) and Pan (Chimpanzees and Bonobos), but excludes the genus Gorilla (gorillas). The term was originally introduced by John Edward Gray (1824), long before any details on the speciation of Pan and Homo were known. Gray's tribe Hominini by definition includes both Pan and Homo.
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However, because the radical is so reactive, there is likely not enough time for transport to the cell surface (mean diffusion distance of 4.5 nm). Thus, direct effects to organisms of externally generated hydroxyl radicals are expected to be minimal. Indirectly, the hydroxyl radical can result in significant biogeochemical changes in marine systems by influencing the cycling of dissolved organic matter and trace metal speciation.
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Hershkovitz proposed that the separation of the two species happened in the Pleistocene at the height of the Atrato River, where it intersected the Cauca-Magdalena. At that time, the area was covered by a sea, which created a geographic barrier that caused the species to diverge through the process of allopatric speciation. Today, the two species are principally separated by the Atrato River.
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Figure 6b: A common fruit fly (Drosophila melanogaster) William R. Rice and George W. Salt found experimental evidence of sympatric speciation in the common fruit fly. They collected a population of Drosophila melanogaster from Davis, California and placed the pupae into a habitat maze. Newborn flies had to investigate the maze to find food. The flies had three choices to take in finding food.
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Data suggests division of the genus into three species: the annual wild species S. sylvestre, the perennial wild species S. strictum including many subspecies, and S. cereale with cultivated and weedy rye subspecies.Ren, T., Chen, F., Zou, Y., Jia, Y., Zhang, H., Yan, B., & ... Scoles, G. (2011). Evolutionary trends of microsatellites during the speciation process and phylogenetic relationships within the genus Secale. Genome, 54(4), 316–326.
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The reaction to produce fluoroantimonic acid results in formation of the fluoronium ion as a major species in equilibrium: :SbF5 \+ 2 HF ⇄ + H2F+ However, the speciation of "fluoroantimonic acid" is complex, and consists of a mixture of HF-solvated protons, [ (e.g., H3F2+), and SbF5-adducts of fluoride (e.g., Sb4F21–). Thus, the formula "[H2F]+SbF6–" is a convenient but oversimplified approximation of the true composition.
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Evolutionary biologists and population geneticists have been exploring varying theories and models for explaining population structure. Yoichi Ishida compares two important theories of isolation by distance and clarifies the relationship between the two. According to Ishida, Sewall Wright's isolation by distance theory is termed ecological isolation by distance while Gustave Malécot's theory is called genetic isolation by distance. Isolation by distance is distantly related to speciation.
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Species flocks are indicative of adaptive radiation. Antarctic fish fit these criteria with modifications in swim bladders, development of AFGPs, loss of HSPs and modifications in oxygen transport while inhabiting the same geographic area. Antarctic fish speciation coincides with the separation of Antarctica from Gondwana, a continent composed of Antarctica, Australia, South America and Africa. The temperate, shallow seas hosted a variety of marine life.
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Technologies such as genomic microarrays, also called array comparative genomic hybridization (array CGH), are used to detect chromosomal abnormalities, such as microduplications, in a high throughput fashion from genomic DNA samples. In particular, DNA microarray technology can simultaneously monitor the expression levels of thousands of genes across many treatments or experimental conditions, greatly facilitating the evolutionary studies of gene regulation after gene duplication or speciation.
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Other Drosophila research on reinforcement has been from laboratory experiments and is discussed below. On the east coast of Australia, D. serrata shares a zone of sympatric overlap with the closely relates species D. birchii. The species exhibits reproductive character displacement, with sexual selection operating on the hydrocarbons of the flies cuticle. Reinforcement appears to be driving their speciation in nature, supported by simulated experimental laboratory populations.
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These traits may promote speciation through increased mutation and selection events as molecular evolution scales with metabolic rate (Gillooly et al. 2005Gillooly JF, Allen AP, West GB, & Brown JH (2005) The rate of DNA evolution: Effects of body size and temperature on the molecular clock. Proceedings of the National Academy of Sciences of the United States of America 102(1):140-145.) and thus with body size.
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Syntelog: a special case of gene homology where sets of genes are derived from the same ancestral genomic region. This may arise from speciation events, or through whole or partial genome duplication events (e.g. polyploidy). This term is distinct from ortholog, paralog, in-paralog, out-paralog, and xenolog because it refers only to genes' evolutionary history evidenced by sequence similarity and relative genomic position.
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This variation leads to a higher likelihood of ecological niche specialization and the evolution of reproductive isolation. Centrifugal speciation has been largely ignored in the scientific literature. Nevertheless, a wealth of evidence has been put forth by researchers in support of the model, much of which has not yet been refuted. One example is the possible center of origin in the Indo- West Pacific.
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Islands are not the only geographic locations that have endemic species. South America has been studied extensively with its areas of endemism representing assemblages of allopatrically distributed species groups. Charis butterflies are a primary example, confined to specific regions corresponding to phylogenies of other species of butterflies, amphibians, birds, marsupials, primates, reptiles, and rodents. The pattern indicates repeated vicariant speciation events among these groups.
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Lin, P., M. Chen, L. Guo. 2012. Speciation and transformation of phosphorus and its mixing behavior in the Bay of St. Louis estuary in the northern Gulf of Mexico, in Geochimica et Cosmochimica Acta 87:283-298.Blain, CA, CR Edwards. 2002. Development of a forecast capability for coastal embayments of the Mississippi Sound, in OCEANS '02 MTS/IEEE 3:1501-1508Blain, CA, J Veeramony. 2002.
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Barriers to gene flow need not always be physical. Sympatric speciation happens when new species from the same ancestral species arise along the same range. This is often a result of a reproductive barrier. For example, two palm species of Howea found on Lord Howe Island were found to have substantially different flowering times correlated with soil preference, resulting in a reproductive barrier inhibiting gene flow.
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This dorid nudibranch occurs in the eastern Pacific, from Barkley Sound, British Columbia to Baja California, Mexico. It has been confused with Diaulula boreopacifica which has a more northerly range and also occurs in Japan and Russia.Lindsay, T., Kelly, J., Chichvarkhin, A., Craig, S., Kajihara, H., Mackie, J & Valdés, A. (2016). Changing spots: pseudocryptic speciation in the North Pacific dorid nudibranch Diaulula sandiegensis (Cooper, 1862) (Gastropoda: Heterobranchia).
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Psychological capacities for mediating behavior rather than behaviors per se were the traits favored by selection during EEA and the selection favoring psychological capacities most parsimoniously accounts for human behavioral plasticity. Response: There is the possibility that Homo sapiens is still undergoing genetic change. Since Homo sapiens is recent in origin, speciation may be continuing both in terms of physical traits and mental conditions.Darwinian Psychiatry, p.
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Evolution generally occurs at a scale far too slow to be witnessed by humans. However, bird species are currently going extinct at a far greater rate than any possible speciation or other generation of new species. The disappearance of a population, subspecies, or species represents the permanent loss of a range of genes. Another concern with evolutionary implications is a suspected increase in hybridization.
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When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis. Cladogenesis is the process by which a species splits into two distinct species, rather than one species gradually transforming into another.Gould, Stephen Jay, & Eldredge, Niles (1977). "Punctuated equilibria: the tempo and mode of evolution reconsidered." Paleobiology 3 (2): 115-151. (p.
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However, the punctuational equilibrium model may still be inferred from both the observation of stasis and examples of rapid and episodic speciation events documented in the fossil record. Dawkins also emphasizes that punctuated equilibrium has been "oversold by some journalists",Dawkins, Richard (1996). The Blind Watchmaker, p. 250-251. but partly due to Eldredge and Gould's "later writings".Dawkins, Richard (1996). The Blind Watchmaker, p. 241.
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Their diversity in the African Great Lakes is important for the study of speciation in evolution. Many cichlids introduced into waters outside of their natural range have become nuisances. All cichlids have some form of parental care for their eggs and fry. That parental care may come in the form of guarding the eggs and fry or it may come in the form of mouthbrooding.
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Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within the final two sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation.
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On the contrary, evidence suggests that horizontal gene transfer has bolstered the diversification and speciation of many bacteria. Horizontal gene transfer is often detected via DNA sequence information. DNA segments obtained by this mechanism often reveal a narrow phylogenetic distribution between related species. Furthermore, these regions sometimes display an unexpected level of similarity to genes from taxa that are assumed to be quite divergent.
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Schowalteria is a genus of extinct mammal from the Cretaceous of Canada. It is the earliest known representative of Taeniodonta, a specialised lineage of non-placental eutherian mammals otherwise found in Paleocene and Eocene deposits. It is notable for its large size, being among the largest of Mesozoic mammals, as well as its speciation towards herbivory, which in some respects exceeds that of its later relatives.
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Their main use is for preconcentration of metal ions in a dilute solution.Apte, S. C.; Batley, G. E., "Trace metal speciation of labile chemical species in natural waters and sediments: non-electrochemical approaches", IUPAC Ser. Anal. Phys. Chem. Environ. Syst. 1995, 3, 259-306.Garg, B. S.; Sharma, R. K.; Bhojak, N.; Mittal, S., "Chelating Resins and Their Applications in the Analysis of Trace Metal Ions", Microchem.
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This dorid nudibranch occurs in the northern Pacific, from Northern California to Alaska, Japan and Russia. It has been confused with Diaulula sandiegensis which has a more southerly range from California south to Baja California, Mexico.Lindsay, T., Kelly, J., Chichvarkhin, A., Craig, S., Kajihara, H., Mackie, J & Valdés, A. (2016). Changing spots: pseudocryptic speciation in the North Pacific dorid nudibranch Diaulula sandiegensis (Cooper, 1862) (Gastropoda: Heterobranchia).
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"Macrolides from the scent glands of the tropical butterflies Heliconius cydno and Heliconius pachinus". Organic and Bimolecular Chemistry, 2007. In fact, it has been suggested that wing preference patterns in mating may limit hybridization, a preference which is also known to limit hybridization between H. cydno and H. pachinus, which is another closely related species. Thus, divergent coloring (and therefore, mimicry), contributes to sympatric speciation.
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Lake Bermin (sometimes spelled Bemin or Beme) is a small lake in the volcanic chain in the Southwest Region of Cameroon. It is a volcanic lake with a diameter of about Martin; Cutler; Friel; Touokong; Coop; and Wainwright (2015). Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422.
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From skin impressions found with fossils, it has been determined that the skin of many titanosaurians was armored with a small mosaic of small, bead-like scales surrounding larger scales. While most titanosaurs were very large animals, many were fairly average in size compared to other giant dinosaurs. Some island-dwelling dwarf titanosaurs, such as Magyarosaurus, were probably the result of allopatric speciation and insular dwarfism.
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These factors directly impacted the health of Manila Bay's waters. Aside from oil spills, trace metals such as copper, cadmium and zinc at the surface of the waterVelasquez I., Jacinto, G.S., and Valera, F.S., (2002). The speciation of dissolved copper, cadmium and zinc in Manila Bay, Philippines. Marine Pollution Bulletin 45, pp 210-217 were found at the bay coming from sea-based and land-based (e.g.
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In an apparent example of emerging speciation, some of the Menoptra fled underground, adapting to a subterranean environment and calling themselves the Optera. This species have lost the ability to fly, and resemble upright caterpillars, indicating that they had evolved through neoteny. They also have larger eyes than their Menoptra brethren. However, they have numerous arms and appear to 'hop' in a stylised way.
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The process of genome stabilization during hybrid speciation and introgression. Both ecological selection pressures and selection to avoid intrinsic incompatibilities mould hybrid genomes. Depending on the balance between beneficial alleles and incompatibilities hybridisation can result either in an admixed taxon that is reproductively isolated from both parent taxa, or local introgression into a taxon that remains distinct in spite of occasional gene flow. RI abbreviates reproductive isolation.
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Lewis' first publication was with Carl Epling in 1940 which covered the distributions of three species pairs in Californian chaparral and coastal sage scrub communities. In this paper he shows his first interest in plant distributions as they relate to speciation. His next publications with Epling followed in 1942. One was taxonomic in nature, and concerned itself with the genus Monarda in the Lamiaceae.
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Apis florea and Apis andreniformis are small honey bees of southern and southeastern Asia. They make very small, exposed nests in trees and shrubs. Their stings are often incapable of penetrating human skin, so the hive and swarms can be handled with minimal protection. They occur largely sympatrically, though they are very distinct evolutionarily and are probably the result of allopatric speciation, their distribution later converging.
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In population genetics and population ecology, population size (usually denoted N) is the number of individual organisms in a population. Population size is directly associated with amount of genetic drift, and is the underlying cause of effects like population bottlenecks and the founder effect. Genetic drift is the major source of decrease of genetic diversity within populations which drives fixation and can potentially lead to speciation events.
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Chemistry and sibling speciation in the lichen- forming fungi: Ecological and biological considerations. The Bryologist 89:123-131. Apothecia in Niebla homalea appear less frequent and develop more towards the apex of branches, often on short side branchlets, and are compressed to where they attach to the branch, the branch itself also flattened at the junction. Additionally, these short side branchlets often appear without apothecia.
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The pKa of the hydroxyl group has been found, by means of 13C NMR spectroscopy, to be 14.4. The speciation diagram shows that solutions of citric acid are buffer solutions between about pH 2 and pH 8. In biological systems around pH 7, the two species present are the citrate ion and mono-hydrogen citrate ion. The SSC 20X hybridization buffer is an example in common use.
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Despite burnetiid species occurrences being rare and discovered from different zones, the family was species-rich, with one specimen per genus, suggesting that they had high rates of speciation and extinction. Hill in siliciclastic strata (mud or siltstones capped by solid sandstone) of Teekloof or Abrahamskraal formation (Beaufort Group) of the Main Karoo Basin. Karoo National Park near Beaufort West, Western Cape Province, South Africa.
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Gavin Wildridge Johnstone (1941-1987) was an Australian ornithologist who grew up and was educated in Scotland. He completed his PhD thesis on the ecology and behaviour of Black Grouse, at the University of Aberdeen in 1969. He moved to Australia in 1969 to participate in the 1970 Australian National Antarctic Research Expedition (ANARE). There he wintered on Macquarie Island and worked on speciation in Giant Petrels.
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That changed when, in 1882, Baker contributed the first species accepted into the genus from Madagascar. The degree of speciation then turned to Madagascar, where the count of species far exceeds those on the mainland. In 1907, Costantin and Bois constructed the first monograph, of Pachypodium, in which they enumerated 17 species, where ten were from Madagascar and seven were from continental southern Africa.
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TreeFam (Tree families database) is a database of phylogenetic trees of animal genes. It aims at developing a curated resource that gives reliable information about ortholog and paralog assignments, and evolutionary history of various gene families. TreeFam defines a gene family as a group of genes that evolved after the speciation of single-metazoan animals. It also tries to include outgroup genes like yeast (S.
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The black metaltail (Metallura phoebe) is a species of hummingbird in the family Trochilidae. It is endemic to Peru and possibly stretches to northern Chile and Bolivia. Within the latter two countries it is possible that there may be speciation or separate subspecies but more research is required. Its natural habitats are subtropical or tropical moist montane forest and subtropical or tropical high-altitude shrubland.
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Inparanoid is an algorithm that finds orthologous genes and paralogous genes that arose—most likely by duplication—after some speciation event. Such protein-coding genes are called in-paralogs, as opposed to out-paralogs (which arose prior to a species split). Inparanoid (with varying capitalization) may refer to a program that uses the INPARANOID algorithm, or to the derived database of orthologous clusters of genes.
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Speciation in the group is thought to have begun with the ancestral species originating somewhere in southern China, making L. steerii the basal species. The lineage consisting of L. ripponi and L. phoenicea are thought to have had a split in the Pleistocene (0.07–1.88 Ma) with a similar split of the other lineage leading to L. bugunorum and L. omeiensis separated by the Hengduan mountains.
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The presence of a savanna corridor—even if fragmented—would have allowed for savanna-dwelling fauna (as well as early humans) to disperse between Sundaland and the Indochinese biogeographic region; emergence of a savanna corridor during glacial periods and subsequent disappearance during interglacial periods would have facilitated speciation through both vicariance (allopatric speciation) and geodispersal. Morley and Flenley (1987) and Heaney (1991) were the first to postulate the existence of a continuous corridor of savanna vegetation through the center of Sundaland (from the modern Malaysian Peninsula to Borneo) during the last glacial period, based on palynological evidence. Using the modern distribution of primates, termites, rodents, and other species, other researchers infer that the extent of tropical forest contracted—replaced by savanna and open forest —during the last glacial period. Vegetation models using data from climate simulations show varying degrees of forest contraction; Bird et al.
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In the 2010s Filardi was part of a team sponsored by Conservation International and the National Science Foundation to map the process of speciation in the Solomon Islands. The group identified the Solomons frogmouth as a new genus of bird.Cleere, Kratter, Steadman, Braun, Huddleston, Filardi and Dutson. 2007. A new genus of frogmouth (Podargidae) from the Solomon Islands – results from a taxonomic review of Podargus ocellatus inexpectatus Hartert 1901.
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Scale economies occur through reproduction and the duplicative growth of species population. Scope economies, on the other hand, come through speciation, the evolutionary emergence of new species, based on the same platform as individual species. Finally, knowledge economies arise through the accumulative encoding, refining and sharing of survival information genetically overtime in DNA. The Sustainable Production Platform principle allows businesses to emulate nature's platform approach in manufacturing and generate similar economies.
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Many agriculturally important plants of the genus Brassica are also tetraploids. Polyploidization can be a mechanism of sympatric speciation because polyploids are usually unable to interbreed with their diploid ancestors. An example is the plant Erythranthe peregrina. Sequencing confirmed that this species originated from E. × robertsii, a sterile triploid hybrid between E. guttata and E. lutea, both of which have been introduced and naturalised in the United Kingdom.
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Sanders, K. L., Mumpuni, Lee M. S. Y. 2010 Uncoupling ecological innovation and speciation in sea snakes (Elapidae, Hydrophiinae, Hydrophiini. J. Evol. Biol. 23 (12):2685-93 An analysis of the population in 2014 found strong evidence of deep divergence and genetic isolation across the geographical range, supporting a division of the species to Indian Ocean and West Pacific groups and high likelihood of cryptic taxa within those groups.
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It acted as an overpass for land-dwellers to move from Asia to North America, and vice versa. Evidence for this was in the speciation of troodontids in Asia and North America respectively after the Bering Land Bridge broke off in the early Late Cretaceous. The land bridge was then repeatedly inundated and exposed since the breakup of Laurasia, contributing to the episodic exchange of fauna involving dinosaurs and mammals alike.
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Male and female reproductive organs are homologous if they develop from the same embryonic tissue, as do the ovaries and testicles of mammals including humans. Sequence homology between protein or DNA sequences is similarly defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event (orthologs) or a duplication event (paralogs). Homology among proteins or DNA is inferred from their sequence similarity.
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Maynard Smith suggested that homozygous individuals may, under particular environmental conditions, have a greater fitness than those with alleles heterozygous for a certain trait. Under the mechanism of natural selection, therefore, homozygosity would be favoured over heterozygosity, eventually leading to speciation. Sympatric divergence could also result from the sexual conflict.Thierry Lodé La guerre des sexes chez les animaux Eds O Jacob, Paris, 2006 Disruption may also occur in multiple-gene traits.
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The medium ground finch (Geospiza fortis) is showing gene pool divergence in a population on Santa Cruz Island. Beak morphology conforms to two different size ideals, while intermediate individuals are selected against. Some characteristics (termed magic traits) such as beak morphology may drive speciation because they also affect mating signals. In this case, different beak phenotypes may result in different bird calls, providing a barrier to exchange between the gene pools.
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Mayr's hypothesis was popular and consequently quite influential, but is now widely disputed. The first to propose what is now the most pervasive hypothesis on how sympatric speciation may occur was John Maynard Smith, in 1966. He came up with the idea of disruptive selection. He figured that if two ecological niches are occupied by a single species, diverging selection between the two niches could eventually cause reproductive isolation.
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Mallet et al. (2002) claims that the new non-spatial definition is lacking in an ability to settle the debate about whether sympatric speciation regularly occurs in nature. They suggest using a spatial definition, but one that includes the role of dispersal, also known as cruising range, so as to represent more accurately the possibility for gene flow. They assert that this definition should be useful in modeling.
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In 2013, a study published in Science estimated there to be 5 ± 3 million extant species on Earth. Another study, published in 2011 by PLoS Biology, estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. Some 250,000 valid fossil species have been described, but this is believed to be a small proportion of all species that have ever lived. Global biodiversity is affected by extinction and speciation.
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Sylvilagus palustris hefneri has been isolated to the Keys by the rise in sea level and human inhabitation to the local area.Reed, Robert N. "An Ecological Risk Assessment of Nonnative Boas and Pythons as Potentially Invasive Species in the United States." Risk Analysis: An International Journal 25.3 (2005): 753-766. This isolation may be the cause for the speciation from the Upper Keys marsh rabbit, Sylvilagus palustris paludicola.
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Kirsten Bomblies is an American biological researcher. Her research focuses primarily on species in the Arabidopsis genus, particularly Arabidopsis arenosa. She has studied processes related to speciation and hybrid incompatibility, and currently focuses on the adaptive evolution of meiosis in response to climate and genome change. She was Assistant Professor and then Thomas D. Cabot Associate Professor of Organismic and Evolutionary Biology at Harvard University from 2009 until 2015.
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Ectomycorrhizas may have evolved with the diversification of plants and the evolution of conifers and angiosperms. Arbuscular mycorrhizas may thus have been a driving force in the plant colonization of land, while ectomycorrhizas may have arisen either in response to further speciation as the earth's climate became more seasonal and arid, or perhaps simply in response to nutritionally deficient habitats.Allen, Michael F. The ecology of mycorrhizae. Cambridge University Press, 1991.
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The Grande Coupure, or "great break" in continuity,also termed the MP 21 event. with a major European turnover in mammalian fauna about 33.5 Ma, marks the end of the last phase of Eocene assemblages, the Priabonian, and the arrival in Europe of Asian species. The Grande Coupure is characterized by widespread extinctions and allopatric speciation in small isolated relict populations.Called "dispersal-generated origination" in Hooker et al.
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Despeciation is the loss of a unique species of animal due to its combining with another previously distinct species. It is the opposite of speciation and is much more rare. It is similar to extinction in that there is a loss of a unique species but without the associated loss of a biological lineage. Despeciation has been noted in species of butterflies, sunflowers, mosquitoes, fish, wolves, and even humans.
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This has major evolutionary implications since it may argue for sympatric speciation. Raids can jeopardize host colony survival, therefore exerting a strong selection pressure upon the hosts. Reciprocally, there is some evidence that hosts also exert a selection pressure on their parasites in return, since resistance by host colonies might prevent enslavement. Coevolutionary processes between slave-making ant species and their hosts then can escalate to an evolutionary arms race.
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The vertebrate host is the first criterion used for speciation and may be sufficient alone to determine the subgenus as in Ophidiella and Vinckeia. The morphological features of the parasite itself most commonly used to describe a species include the number of pigment granules, the degree of encirclement of the host nucleus, the size of the parasite, the degree of host nucleus displacement and the degree of host cell enlargement.
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Evidence from hepatics on the history of the British flora. Journal of Ecology 38(2): 320–344.. He tried to evaluate how many of the extant British liverworts had survived Pleistocene glaciations in situ and how many, in contrast, were postglacial migrants from southern latitudes. Almost two decades before the theory of Pleistocene refugia was proposed by Jürgen Haffer for the AmazonHaffer, Jürgen. 1969. Speciation in Amazonian forest birds.
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Phylogenesis suggest that DOPEY2 can be traced back to a common ancestor of animals and fungi due to its highly conserved C-terminal domain DOPEY2 has 84 known orthologs and 158 speciation nodes in the gene tree. The most similar orthologs being in the chimpanzee (Pan troglodytes), dog (Canis familiaris), cow (Bos Taurus), as well as the rat and mouse (Rattus norvegicus and Mus musculus). The only known paralog is DOPEY1.
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Genetic analysis was also conducted on two mtDNA sites (416 base pairs from cytochrome C and 593 base pairs from cytochrome oxidase ) to "control for the confounding effects of time since divergence among allopatric populations". In an additional study, the researchers studied two gall wasp species B. treatae and Disholcaspis quercusvirens and found strong morphological and behavioral variation among host-associated populations. This study further confounded prerequisites to speciation.
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R. juglandis belongs to the genus Rhagoletis and the family Tephritidae.juglandis It is closely related to Rhagoletis suavis (Loew, 1862), Rhagoletis completa (Cresson, 1929), Rhagoletis boycei (Cresson, 1929), Rhagoletis zoqui (Bush, 1966), and Rhagoletis ramosae (Hernández-Ortiz, 1985). These species do not generally overlap in geographic range in North America, but there has been some described sympatry and parapatry. R. suavis group flies have history that is consistent with allopatric speciation.
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Its subtitle famously asks, "Why are there so many kinds of animals?", and the address attempts to answer this question by suggesting theoretical bounds to speciation and niche overlap. For the purposes of understanding limiting similarity, the key portion of Hutchinson's address is the end where he presents the observation that a seemingly ubiquitous ratio (1.3:1) defines the upper bound of morphological character similarity between closely related species.Hutchinson, GE. 1959.
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Dicynodont species diversified greatly in this biozone, a speciation trend that continued with this group until the end of the Permian period. A pareiasaur species, Pareiasaurus serridens, various subspecies of the temnospondyl amphibian Rhinesuchus, the fishes Namaichthys and Atherstonia, and fossil plant material of Glossopteris and Dadoxylon have been found. Finally, vertebrate burrows left by Diictodon as previously discussed, vertebrate trackways left by various therapsid species, and coprolites have been recovered.
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BEAST (Bayesian Evolutionary Analysis by Sampling Trees) provides tools for reconstructing ancestral geographic locations from observed sequences annotated with location data using Bayesian MCMC sampling methods. Diversitree is an R package providing methods for ancestral state reconstruction under Mk2 (a continuous time Markov model of binary character evolution). and BiSSE (Binary State Speciation and Extinction) models. Lagrange performs analyses on reconstruction of geographic range evolution on phylogenetic trees.
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Orang Utan (Pongo pygmaeus) is among the most iconic animals of Borneo and the flagship of rainforest conservation in South-East Asia. Borneo is the third largest island in the world. In prehistoric times it was connected to the Asian mainland due to geological and climate changes. During the recent ice ages of the Pleistocene and the Holocene separation from the mainland caused extinctions and speciation of fauna on the island.
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This model describes a situation where after initial colonization (or speciation) each new species pre-empts more than 50% of the smallest remaining niche. In a Dominance preemption model of niche apportionment the species colonize random portion between 50 and 100% of the smallest remaining niche, making this model stochastic in nature. A closely related model, the Geometric Series,May, R. M. (1975). Patterns of species abundance and diversity.
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Gottlieb using starch gel electrophoresis, determined that indeed C. lingulata had a high degree of genetic similarity to C. biloba, with fewer alleles and reduced heterozygosity. Subsequent studies confirmed a sister species relationship using chloroplast DNA as well as nucleotide sequences of the gene phosphoglucose isomerase. Gottlieb stated that this species pair, too, arose from quantum speciation. Layia discoidea'Layia glandulosa Similar work was done with species pairs in the genus Layia.
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The theory of island biogeography. Princeton 1967. According to Ernst Mayr, :"The person who more than anyone else deserves credit for reviving an interest in the ecological significance of species was David Lack... It is now quite clear that the process of speciation is not completed by the acquisition of isolating mechanisms but requires also the acquisition of adaptations that permit co-existence with potential competitors."Mayr, Ernst (1985).
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One hypothesis is that during the speciation event in anagenetic evolution, the original populations will increase quickly, and then rack up genetic variation over long periods of time by mutation and recombination in a stable environment. Other factors such as selection or genetic drift will have such a significant effect on genetic material and physical traits that a species can be acknowledged as being different from the previous.
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Salvelinus taranetzi, also known as the Taranets char,Alexander G. Osinov, Anna L. Senchukova, Nikolai S. Mugue, Sergei D. Pavlov, Igor A. Chereshnev (2015) Speciation and genetic divergence of three species of charr from ancient Lake El'gygytgyn (Chukotka) and their phylogenetic relationships with other representatives of the genus Salvelinus Biological Journal of the Linnean Society 116, 63–85. is a species of salmonid fish native to Chukotka, Northeast Russia.
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In doing so, he questioned the over-riding importance of random genetic drift advocated by King, Jukes, and Kimura. With Professor James J Murray Jnr (University of Virginia), he carried out an extensive series of studies on speciation in land snails of the genus Partula inhabiting the volcanic islands of the Eastern Pacific. These studies helped illuminate the genetic changes that take place during the origin of species.
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Complex histories of repeated gene flow in Cameroon crater lake cichlids cast doubt on one of the clearest examples of sympatric speciation. Evolution 69-6: 1406–1422. The myika is threatened because of pollution and sedimentation due to human activities. It is potentially also threatened by large emissions of carbon dioxide (CO2) from the lake's bottom (compare Lake Nyos), although studies indicate that Barombo Mbo lacks excess amounts of this gas.
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Herbivores: between plants and predators. Blackwell Science, London, UK. The coevolution that occurs between plants and herbivores that ultimately results in the speciation of both can be further explained by the Red Queen hypothesis. This hypothesis states that competitive success and failure evolve back and forth through organizational learning. The act of an organism facing competition with another organism ultimately leads to an increase in the organism's performance due to selection.
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The spawning season for this species is relatively short with high sensitivity to temperature changes. Global temperature changes are at an unprecedented rise, which could eventually lead to a global shift in water temperature. This could highly affect the spawning season for the brook stickleback species. Protection of this species should be on high priority because this species has led scientist in significant breakthroughs in sympatric and allopathic speciation.
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Paracatenula host their symbionts within bacteriocytes in the trophosome. These bacteria, named Ca. Riegeria, belong to the lineage alphaproteobacteria forming a monophyletic group within the order Rhodospirillales and the family [Rhodospirillaceae]. The co-speciation between host and bacteria suggests a strict vertical transmission of the bacteria in which the endosymbionts are directly transferred from parents to their offspring. The symbiosis is shown to be beneficial for both partners.
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The speciation occurred around 10 million years ago, therefore its distribution cannot be due to continental drift, the Americas having separated from Africa much earlier. The species probably originates from seeds dispersed by migrating birds. It has bright orange-red, scentless flowers with abundant nectar that are typical of other bromeliads having birds as pollinators, although no actual sighting of birds pollinating the species has been recorded yet.
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In the novel, a new form of endogenous retrovirus has emerged, SHEVA. It controls human evolution by rapidly evolving the next generation while it is in the womb, leading to speciation. The novel follows several characters as the "plague" is discovered as well as the panicked reaction of the public and the US government to the disease. Built into the human genome are non-coding sequences of DNA called introns.
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These drongos will sometimes steal insect prey caught or disturbed by other foragers in the flock and another idea is that vocal mimicry helps them in diverting the attention of smaller birds to aid their piracy. They are diurnal but are active well before dawn and late at dusk. Owing to their widespread distribution and distinctive regional variation, they have become iconic examples of speciation by isolation and genetic drift.
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Ernst Mayr argued that geographic isolation was needed to provide sufficient reproductive isolation for new species to form. Ernst Mayr's key contribution to the synthesis was Systematics and the Origin of Species, published in 1942. It asserted the importance of and set out to explain population variation in evolutionary processes including speciation. He analysed in particular the effects of polytypic species, geographic variation, and isolation by geographic and other means.
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Evolutionary developmental biology relates the evolution of form to the precise pattern of gene activity, here gap genes in the fruit fly, during embryonic development. Ernst Mayr recognised the key importance of reproductive isolation for speciation in his Systematics and the Origin of Species (1942). W. D. Hamilton conceived of kin selection in 1964. This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today.
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These factors have favoured genetic isolation and rapid speciation, producing many lineages with restricted ranges. The living members of the Diplopoda are divided into sixteen orders in two subclasses. The basal subclass Penicillata contains a single order, Polyxenida (bristle millipedes). All other millipedes belong to the subclass Chilognatha consisting of two infraclasses: Pentazonia, containing the short-bodied pill millipedes, and Helminthomorpha (worm-like millipedes), containing the great majority of the species.
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Common and Antarctic minke whales diverged from each other in the Southern Hemisphere 4.7 million years ago, during a prolonged period of global warming in the early Pliocene which disrupted the Antarctic Circumpolar Current and created local pockets of upwelling, facilitating speciation by fragmenting populations. The radiation of common minke whales into the Northern Hemisphere occurred rapidly about 1.5 million years ago during a period of cooling in the Pleistocene.
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Meinrat O. Andreae studied chemistry, mineralogy, and geochemistry at the Universities of Karlsruhe and Göttingen. In his diploma thesis, he studied the chemical composition and isotope geochemistry of highly metamorphic rocks of southern Norway. In 1977, he completed his PhD in oceanography from the Scripps Institution of Oceanography at the University of California at San Diego. In his doctoral thesis, he examined the chemical speciation of arsenic in the ocean.
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The Sangha forest robin (Stiphrornis erythrothorax sanghensis) is a subspecies of the forest robin that is endemic to south-western Central African Republic, but may also occur in adjacent parts of DR Congo, Cameroon and Republic of the Congo. It was only discovered in 1996, and scientifically described in 1999.Beresford, P. & Cracraft, J. (1999). Speciation in African forest robins (Stiphrornis): species limits, phylogenetic relationships, and molecular biogeography.
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T.F. Duda, Jr. & A.J. Kohn (2005), Species-level phylogeography and evolutionary history of the hyperdiverse marine gastropod genus Conus, Molecular Phylogenetics and Evolution 34:257-272.T.F. Duda, Jr. & E. Rolan (2005), Explosive radiation of Cape Verde Conus, a marine species flock, Molecular Ecology 14:267-272.B. Vallejo, Jr. (2005), Inferring the mode of speciation in the Indo-West Pacific Conus (Gastropoda: Conidae), Journal of Biogeography 32:1429-1439.
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Thus hybrid genomes are highly dynamic and may undergo rapid evolutionary change, including genome stabilization in which selection against incompatible combinations results in fixation of compatible ancestry block combinations within the hybrid species. The potential for rapid adaptation or speciation makes hybrid genomes a particularly exciting subject of in evolutionary biology. The article summarizes how introgressed alleles or hybrid species can establish and how the resulting hybrid genomes evolve.
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Potential evolutionary outcomes of hybridization. While most hybridization events are evolutionary dead ends, hybridization may also lead to speciation reversal where two taxa merge into one or form a hybrid zone between parapatric taxa. Alternatively, only one species may disappear through genetic swamping if introgression is highly asymmetrical. When one or few heterospecific alleles are advantageous these can also introgress into one of the parent species’ genomes through repeated backcrossing.
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His first publication was with Carl Epling in 1940 covered the distributions of three species pairs in Californian chaparral and coastal sage scrub communities. In this paper he shows his first interest in plant distributions as they relate to speciation. His next publications with Epling followed in 1942. One was taxonomic in nature, a continuing interest of his, and concerned itself with the genus Monarda in the Lamiaceae.
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Speciation via polyploidy: A diploid cell undergoes failed meiosis, producing diploid gametes, which self- fertilize to produce a tetraploid zygote. Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes. Huge explosions in angiosperm species diversity appear to have coincided with ancient genome duplications shared by many species.de Bodt et al.
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Hydrochloric acid is the salt of the hydronium ion, H3O+ and chloride. It is usually prepared by treating HCl with water. : HCl + H2O -> H3O^+ + Cl^- However, the speciation of hydrochloric acid is more complicated than this simple equation implies. The structure of bulk water is infamously complex, and likewise, the formula H3O+ is also a gross oversimplification of the true nature of the solvated proton, H+(aq), present in hydrochloric acid.
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The ranges of the four species do not overlap, so this genus is an example of probable allopatric speciation. Two species are island endemics: the Buru mountain pigeon is endemic to the Maluku Islands, and the pale mountain pigeon is endemic to the Solomon Islands. The Papuan mountain pigeon has a range in between the others; it lives on the island of New Guinea and on nearby smaller islands.
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Given that small changes in toolbox genes can cause significant changes in body structures, they have often enabled the same function convergently or in parallel. distal-less generates wing patterns in the butterflies Heliconius erato and Heliconius melpomene, which are Müllerian mimics. In so-called facilitated variation, their wing patterns arose in different evolutionary events, but are controlled by the same genes. Developmental changes can contribute directly to speciation.
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T.F. Duda, Jr. & A.J. Kohn (2005), Species-level phylogeography and evolutionary history of the hyperdiverse marine gastropod genus Conus, Molecular Phylogenetics and Evolution 34:257-272.T.F. Duda, Jr. & E. Rolan (2005), Explosive radiation of Cape Verde Conus, a marine species flock, Molecular Ecology 14:267-272.B. Vallejo, Jr. (2005), Inferring the mode of speciation in the Indo-West Pacific Conus (Gastropoda: Conidae), Journal of Biogeography 32:1429-1439.
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In combination with a small population, as may occur due to recent colonisation, or simply restricted space, genetic drift can occur on shorter timescales than is observable in mainland species. The high levels of endemism on islands have been attributed to these factors. Substantial evidence for speciation due to natal philopatry has been gathered in studies of island-nesting albatross. Genetic difference is most often detected in microsatellites in mitochondrial DNA.
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Cooperative breeding causes the reproductive success of all sexually mature adults to be skewed towards one mating pair. This means the reproductive fitness of the group is held within a select few breeding members and helpers have little to no reproductive fitness. With this system, breeders gain an increased reproductive, while helpers gain an increased inclusive fitness. Cooperative breeding, like speciation, can become a self-reinforcing process for a species.
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The various species of Pachypodium are more or less heavily spined. Species from more arid regions have evolved denser and longer spines. Fog condenses on their spines in the form of dew, which drips down to the ground and increases the amount of moisture that's available to their often shallow roots. The concept of "micro- endemism" plays an important role in this relationship between adaptation mechanisms and speciation.
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Plant species in genera's such as Dubautia, Wilkesia, and Argyroxiphium have also radiated along the archipelago. Other animals besides insects show this same pattern such as the Hawaiian amber snail (Succinea caduca), and ‘Elepaio flycatchers. Tetragnatha spiders have also speciated peripatrically on the Hawaiian islands,Rosemary G. Gillespie & H. B. Croom. (1995). Comparison of speciation mechanisms in web-building and non-web-building groups within a lineage of spiders.
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A host of other Hawaiian endemic arthropod species and genera have had their speciation and phylogeographical patterns studied: the Drosophila grimshawi species complex, damselflies (Megalagrion xanthomelas and Megalagrion pacificum), Doryonychus raptor, Littorophiloscia hawaiiensis, Anax strenuus, Nesogonia blackburni, Theridion grallator, Vanessa tameamea, Hyalopeplus pellucidus, Coleotichus blackburniae, Labula, Hawaiioscia, Banza (in the family Tettigoniidae), Caconemobius, Eupethicea, Ptycta, Megalagrion, Prognathogryllus, Nesosydne, Cephalops, Trupanea, and the tribe Platynini—all suggesting repeated radiations among the islands.
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It resides in Florida and can migrate as far as . Analysis of microsatellite data on the genes of Ae. taeniorhynchus living in the Galapagos Islands show genetic differentiation between coastal and highland mosquito populations. Data indicates minimal gene flow between the populations that only occurs during periods of heightened rainfall. Genetic differences suggest that habitat differences led to driving adaptation and divergence in the species, eventually leading to future speciation.
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The greatest generic diversity is found in the Neotropical realm, while the Holarctic has a smaller number of genera but a high degree of speciation. Some thirteen families are restricted to a single bioregion. The main families have some general habitat preferences: the Baetidae favour warm water; the Heptageniidae live under stones and prefer fast-flowing water; and the relatively large Ephemeridae make burrows in sandy lake or river beds.
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Maggi F. and W. J. Riley, (2010), Mathematical treatment of isotopologue and isotopomer speciation and fractionation in biochemical kinetics, Geochim. Cosmochim. Acta, In the latter two cases, they can describe both stationary and non-stationary fractionation (i.e., variable and inverse fractionation). In general, isotopic effects depend on the number of reactants and on the number of combinations resulting from the number of substitutions in all reactants and products.
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B. P. Hall (1963) "The Francolins, a study in speciation." (PDF) Bulletin of the British Museum 10(2):105-204 The Djibouti spurfowl was originally collected on February 22, 1952 by Captain Albospeyre, the military commander of Tadjoura in the Forêt du Day. It was then described by French ornithologists Jean Dorst and Christian Jouanin later that year as Francolinus ochropectus in L'Oiseau et la Revue française d'Ornithologie.Urban 1986, p.
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The Mirbelioids have had long isolation in Australia from other Fabaceae families. Pultenaea Sm. underwent explosive starburst radiation during the late Miocene, due to aridity. Geographic speciation factors include east vs. west endemism due to increased aridity and the development of the Nullarbor Plain; subgenera Pultenaea and Corrickosa of eastern Australia split along the Winter–Summer rainfall boundary; subclades within Corrickosa diverged due to marine incursions between South Australia and Victoria.
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Catharus is a genus of birds in the thrush family Turdidae. It contains the small, mostly insectivorous or omnivorous migrant thrushes of North America and the nightingale-thrushes of Central and South America. Its closest relative is the wood thrush of the monotypic genus Hylocichla,Winker, Kevin & Pruett, Christin L. (2006): "Seasonal migration, speciation, and morphological convergence in the avian genus Catharus (Turdidae). " Auk 123(4): 1052-1068.
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These Dobzhansky–Muller incompatibilities can therefore also increase the chance of speciation. Certain patterns in the Dobzhansky–Muller incompatibilities can provide information of modes of divergence. For instance, if divergence is due to different selection pressures, thus causing natural selection to act, or to random genetic drift. Therefore, Dobzhansky–Muller incompatibilities can also provide information on the time and type of divergence which can help in phylogenetic studies.
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Mathematical models of biogeography describe speciation (the evolution of new species), the migration of species (animals, fish, birds, or insects) between islands, and the extinction of species. Islands that are friendly to life are said to have a high habitat suitability index (HSI). Features that correlate with HSI include rainfall, vegetative diversity, topographic diversity, land area, temperature, and others. The features that determine are called suitability index variables (SIVs).
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A 2009 phylogenetic analysis based on mitochondrial and nuclear DNA found otherwise, that this species was in fact basal to all other wobbegongs except the northern wobbegong (O. wardi). This result supports the synonymization of Eucrossorhinus with Orectolobus. Molecular clock estimation placed the speciation of the tasselled wobbegong at 11–6 Ma, coinciding with a period of significant geological rearrangement and the formation of coral reef habitats in the region.
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Richea pandanifolia is endemic to Tasmania, as are nine of the 11 species in the genus Richea. Two theories may explain the diversity of Richea species in Tasmania. One proposes that the diversity in endemic Tasmanian Richea species could be due to them being the relics of Gondwanan fragmentation. The other theory proposes that the diversity is the result of speciation subsequent to the breaking up of Gondwana.
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Two mosquito fossils have been found that show very little morphological change in modern mosquitoes against their counterpart from 46 million years ago. These fossils are also the oldest ever found to have blood preserved within their abdomens. The mosquito Anopheles gambiae is currently undergoing speciation into the M(opti) and S(avanah) molecular forms. Consequently, some pesticides that work on the M form no longer work on the S form.
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Honey wasps are species in the genus Brachygastra of the family Vespidae. Brachygastra comprises 17 species of social paper wasps. The ancestral species are thought to have diverged about 32 million years ago within diverse Amazonian rainforest. Subsequent speciation within the genus is thought to have mostly occurred between 23 Ma and 10 Ma, during the time of the Andean uplift when the landscape was significantly altered due to tectonic activity.
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Specifically, he found that increased basal chromosomal numbers in diploid Clarkia were correlated with a xeric habitat, and hypothesized that the genus may have originated at the more mesic ecotone between the Arcto-Tertiary and Madro-Tertiary Floras and spread to more xeric habitats. His fourth paper in 1953 established what he hypothesized to be the primary mode of speciation in Clarkia: > Speciation in Clarkia...has probably resulted from a combination of a > variety of factors. Of these perhaps the most important has been the > differential accumulation in different populations of adapted gene > combinations associated with particular chromosome rearrangements. A by- > product of this accumulation of structural rearrangements has been the > establishment of strong barriers to gene exchange...These phenomena both > suggest that differentiation in Clarkia is often and perhaps usually a rapid > process. In 1954 he published on yet another new species, C. exilis, which was morphologically very similar to C. unguiculata.
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An illustration of the Devonian speciation of lobe-finned fish Acanthostega is seen as part of widespread evolutionary radiation in the late Devonian period, starting with purely aquatic finned tetrapodomorphs, with their successors showing increased air-breathing capability and related adaptions to the jaws and gills, as well as more muscular neck allowing freer movement of the head than fish have, and use of the fins to raise the body of the fish. These features are displayed by the earlier Tiktaalik, which like Ichthyostega showed signs of greater abilities to move around on land, but is thought to have been primarily aquatic. In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish –like Eusthenopteron– exhibited a sequence of adaptations: Panderichthys, suited to muddy shallows; Tiktaalik with limb-like fins that could take it onto land; stem-tetrapods in weed-filled swamps, such as Acanthostega, which had eight-digited feet; and Ichthyostega, with full limbs. Their descendants also included pelagic lobe- finned fish such as coelacanth species.
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Iron-bearing dusts erode from soil and are transported by wind. Although most dust sources are situated in the Northern Hemisphere, the largest dust sources are located in northern and southern Africa, North America, central Asia and Australia. Heterogeneous chemical reactions in the atmosphere modify the speciation of iron in dust and may affect the bioavailability of deposited iron. The soluble form of iron is much higher in aerosols than in soil (~0.5%).
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Anne Daphne Yoder is an American biologist, researcher, and professor in the Department of Biology at Duke University in Durham, North Carolina, United States. Yoder's work includes the study, preservation, and conservation of the multifarious biodiversity found in Madagascar. One of her main research topics focuses on the diverse lemur population found on the island. Specifically, Yoder's research concentrates on assorted geographic factors that lead to varying levels of biological differences in the speciation process.
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Radman's specialty is DNA repair. His work with Evelyn M. Witkin set the basis for the discovery of the SOS response. The SOS response hypothesis was put forward by Radman in 1970 in a letter sent to various researchers, and later published in 1974. With his group he demonstrated the molecular mechanism of speciation by showing that DNA mismatch repair mechanism prevents recombination between similar chromosomes which leads to establishment of genetic barriers between species.
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Taxonomically, its genus and family are extremely complex and are often subject to revision. Indeed, the Procellariidae display a slower rate of speciation compared to other bird groups. Although they are now widely distributed around the world, it appears to have differentiated from the other Procellariiformes over 40-50 million years ago in the Southern Hemisphere. A DNA study revealed that the closest relatives to the petrels are the divers, penguins, and frigatebirds.
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He undertook an expedition to Angola in 1955 and, during the following years, published several papers on geographical variation, speciation, and evolution of African birds. Meise produced 47 parts of Max Schönwetter's handbook Handbuch der Oologie between 1960 and 1992, following Schönwetter's death in 1960. Schönwetter, Max; Meise, Wilhelm Handbuch der Oologie, Akademie Verlag Berlin, 1960-1993. The work consists of 3666 pages and presents in detail all species and subspecies whose eggs are known.
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Danaus petilia, the lesser wanderer, is a species of butterfly in the nymphalid Danainae subfamily. It is a migratory species which is found in AustraliaDanaus petilia, Tree of Life Project and in tropical countries. Previously considered a subspecies of Danaus chrysippus, this species came about through allopatric speciation. The deep sea barrier called Lydekker's Line, located by the Molluccas and the Sahul Shelf, was what separated Danaus petilia from Danaus chrysippus cratippus.
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Large rivers have comparatively more species than small streams. Many relate this pattern to the greater area and volume of larger systems, as well as an increase in habitat diversity. Some systems, however, show a poor fit between system size and species richness. In these cases, a combination of factors such as historical rates of speciation and extinction, type of substrate, microhabitat availability, water chemistry, temperature, and disturbance such as flooding seem to be important.
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One example is rapid turnover of available environment types, like the historical fluctuation of water level in Lake Malawi, a situation that generally favors speciation. A similar situation can be found where closely related species occupy a chain of islands. This will allow any present hybrid population to move into new, unoccupied habitats, avoiding direct competition with parent species and giving a hybrid population time and space to establish. Genetics, too, can occasionally favor hybrids.
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One of the key elements of a sky island is separation by physical distance from the other mountain ranges, resulting in a habitat island, such as a forest surrounded by desert. Some sky islands serve as refugia for boreal species stranded by warming climates since the last glacial period. In other cases, localized populations of plants and animals tend towards speciation, similar to oceanic islands such as the Galápagos Islands of Ecuador.
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Insertion of a SINE upstream of a coding region may result in exon shuffling or changes to the regulatory region of the gene. Insertion of a SINE into the coding sequence of a gene can have deleterious effects and unregulated transposition can cause genetic disease. The transposition and recombination of SINEs and other active nuclear elements is thought to be one of the major contributions of genetic diversity between lineages during speciation.
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She takes him to an ancient museum where "talking rings" tell of a war in the distant past between east and west that lasted 326 years. The atmosphere became so contaminated that it could no longer be safely breathed. Another ring describes humanity's struggle for survival; many decided to move underground, while some returned to the surface. George realizes this was the beginning of the speciation that resulted in the Morlocks and Eloi.
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During his stay in Colombia he met Maria Kluge, a teacher in Bogotá with an interest in Amazonia, marrying her in 1959. During this time he studied the bird faunas of Amazonia and Iran. In close communication with evolutionary biologist Ernst Mayr since the early 1960s, Haffer formulated his ideas on the diversification of birds and the effects of barriers. In 1978 Beryl B. Simpson and Haffer published their analysis of speciation patterns in Amazonia.
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Retrieved on 2011-12-06. assisting bioinformatics in its attempt to solve biological problems. Computational evolutionary biology has enabled researchers to trace the evolution of a large number of organisms by measuring changes in their DNA, rather than through physical taxonomy or physiological observations alone. It has compared entire genomes permitting the study of more complex evolutionary events, such as gene duplication, horizontal gene transfer, and the prediction of factors important in speciation.
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Raparadish, an allopolyploid hybrid between Raphanus sativus and Brassica rapa is grown as a fodder crop. "Raphanofortii" is the allopolyploid hybrid between Brassica tournefortii and Raphanus caudatus. The Raphanobrassica is a fascinating plant, because (in spite of its hybrid nature), it is not sterile. This has led some botanists to propose that the accidental hybridization of a flower by pollen of another species in nature could be a mechanism of speciation common in higher plants.
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From 1939 to 1941 Moore tutored biology at Brooklyn College and from 1941 to 1943 he taught biology at Queens College. In 1943 Moore was hired by Barnard College to teach zoology. He was promoted to full professor in 1950 and was made the chair of the zoology department at Columbia University. Moore received a Fulbright Scholarship in 1952; he and his wife spent a year in Australia using cross-fertilization to study frog speciation.
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Members of the genus Sulfurimonas are found in a variety of different environments which include deep sea-vents, marine sediments, and terrestrial habitats. Their ability to survive in extreme conditions is attributed to multiple copies of one enzyme. Phylogenetic analysis suggests that members of the genus Sulfurimonas have limited dispersal ability and its speciation was affected by geographical isolation rather than hydrothermal composition. Deep ocean currents affect the dispersal of Sulfurimonas spp.
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Heat shock proteins (HSPs) are expressed during exposure to high temperatures and is a characteristic held by most organisms. In some species of nototheniids, this trait is not expressed. The trait is not expressed because of the extreme cold of the Southern Oceans leading to upregulation of Hsp70. HSP expression indicates that regulation of Hsp70 occurred once during speciation, showing that it is a trait of most, if not all Antarctic notothenioids possess.
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If this were true then a simple explanation of why there are more small species on earth would be because they speciate faster. However, a recent analysis by Cardillo and colleagues (2003)Cardillo M, Huxtable JS, & Bromham L (2003) Geographic range size, life history and rates of diversification in Australian mammals. Journal of Evolutionary Biology 16(2):282-288. revealed that body size did not influence the speciation rates of Australia's mammals.
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West-Eberhard has written from the mid-1980s upon the role of "alternative phenotypes," such as polymorphisms, polyphenisms, and context sensitive phenotype life history and physiological traits. This resulted in her 2003 book Developmental Plasticity and Evolution. She argues that such alternative phenotypes are important since they can lead to novel traits, and then to genetic divergence and so speciation. Through alternative phenotypes environmental induction can take the lead in genetic evolution.
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Micromonas diverged early on from the lineage that led to all modern terrestrial plants. Individual species have very similar 16S SSU rRNA gene sequences, a comparison often used to determine microscopic speciation, however, only 90% of different genes are shared between all Micromonas species. This presence or absence of complete genes, compared with only small changes of sequence to specific genes, suggests that Micromonas is the result of intensive horizontal gene transfer.
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Understanding correlations of habitat formation and the migration patterns of organisms at an ecological level allows for explanations of speciation events that may have arisen due to physical geographic isolation events or the incorporation of new refugia to survive unfavorable environmental conditionsTaylor, E. B., McPhail, J.D., 1998. Evolutionary history of an adaptive radiation species in pairs of threespine sticklebacks (Gasterosterus): insights from mitochondrial DNA. Biological Journal of the Linnean Society. 66: 271-291.
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Model of the speciation of Hominoidea over the past 20 million years. The phylogenetic split of Hominidae into the subfamilies Homininae and Ponginae is dated to the middle Miocene, roughly 18 to 14 million years ago. This split is also referenced as the "orangutan–human last common ancestor" by Jeffrey H. Schwartz, professor of anthropology at the University of Pittsburgh School of Arts and Sciences, and John Grehan, director of science at the Buffalo Museum.
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It probably spread across Europe in the wake of the Roman conquest. Possibly, speciation occurred when it colonized southwest India, which was the primary country from which Romans obtained their spices. Since the black rat is a passive traveler, it could have easily traveled to Europe during the trading between Rome and Southwest Asian countries. The black rat in the Mediterranean differs genetically from its Southeast Asian ancestor by having 38 instead of 42 chromosomes.
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Species level evolution in anoles can be very slow. Martinique originally consisted of four tiny islands, which then merged into a single as a result of uplifting. Anoles lived on each of the tiny ancient islands and were isolated six to eight million years ago. Despite this long separation, they did not experience allopatric speciation, as mixed couples of the different Martinique anole populations can successfully reproduce and remain part of a single species.
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Species richness is high among aquatic invertebrates, including 81 species of dragonflies."Mount Nimba". Freshwater Ecoregions of the World, accessed November 10, 2012 The WWF designates the Nimba Range a distinct freshwater ecoregion because of its moderate species richness and high proportion of endemic aquatic species, particularly among fish and amphibians. The Nimba Range's high elevation, its rapids and waterfalls that isolate habitat areas, and the stability of the aquatic environment, have promoted speciation.
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The citron (Citrus medica) is a large fragrant citrus fruit with a thick rind. It is one of the three original citrus fruits from which all other citrus types developed through natural hybrid speciation or artificial hybridization. Though citron cultivars take on a wide variety of physical forms, they are all closely related genetically. It is used widely in Asian cuisine, and also in traditional medicines, perfume, and for religious rituals and offerings.
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Reinforcement is one of the few cases in which selection can favor an increase in prezygotic isolation, influencing the process of speciation directly. This aspect has been particularly appealing among evolutionary biologists. The support for reinforcement has fluctuated since its inception, and terminological confusion and differences in usage over history have led to multiple meanings and complications. Various objections have been raised by evolutionary biologists as to the plausibility of its occurrence.
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Speciation by reinforcement relies directly on selection to favor an increase in prezygotic isolation, and the nature of selection's role in reinforcement has been widely discussed, with models applying varying approaches. Selection acting on hybrids can occur in several different ways. All hybrids produced may be equality low-fitness, conferring a broad disadvantage. In other cases, selection may favor multiple and varying phenotypes such as in the case of a mosaic hybrid zone.
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They first appeared in the Early Paleocene, undergoing numerous speciation events during the Paleocene, and Eocene. Mesonychids fared very poorly at the close of the Eocene epoch, with only one genus, Mongolestes, surviving into the Early Oligocene epoch. Restoration of Mesonyx Mesonychids probably originated in Asia, where the most primitive mesonychid, Yangtanglestes, is known from the early Paleocene. They were also most diverse in Asia where they occur in all major Paleocene faunas.
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Fd is estimated between a hybrid population and the red parent species, and the haplotypes illustrate example individuals in these populations. Hybridization can have many different outcomes. Hybrid speciation results in reproductive isolation against both parent species and genomes that evolve independently from those of the parent species. Introgressive hybridization can transfer important novel variants into genomes of a species that remains distinct from the other taxa in spite of occasional gene flow.
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The evolutionary rate hypothesis argues higher evolutionary rates in the tropics have caused higher speciation rates and thus increased diversity at low latitudes (Cardillo et al. 2005, Weir & Schluter 2007, Rolland et al. 2014). Higher evolutionary rates in the tropics have been attributed to higher ambient temperatures, higher mutation rates, shorter generation time and/or faster physiological processes (Rohde 1992, Allen et al. 2006), and increased selection pressure from other species that are themselves evolving.
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On the other hand, species of wasps pollinate multiple host fig species. Molecular techniques, like microsatellite markers and mitochondrial sequence analysis, allowed a discovery of multiple genetically distinct, cryptic wasp species. Not all these cryptic species are sister taxa and thus must have experienced a host fig shift at some point. These cryptic species lacked evidence of genetic introgression or backcrosses indicating limited fitness for hybrids and effective reproductive isolation and speciation.
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Across Cameroon, and its neighbours to east and west, lies a zone known as the ecotone. This is the northern fringe of the Central African forests, where gallery forest tendrils reach out into the great savannahs of the north. The band of ecotone has, as a consequence, representatives of the flora and fauna of both forest and savannah. It has been highlighted as an area where differences within species may be the precursor to speciation.
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Currently, Pagano is Professor of Economic Policy and Director of the PhD programme in Economics at the University of Siena where he teaches courses on Theory of the Firm, Law and Economics and Political Economy. He teaches also at Central European University, Budapest. In 1997 he was awarded the Kapp Prize for the essay 'Transition and the Speciation of the Japanese Model'Ugo Pagano Journal articles by the European Association for Evolutionary Political Economy.
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Aqion is a hydrochemistry software tool. It bridges the gap between scientific software (such like PhreeqCParkhurst, D.L. and C.A.J. Appelo: User's Guide to PHREEQC (version 2), a computer program for speciation, batch-reaction, one- dimensional transport and inverse geochemical calculations. USGS Water- Resources Investigations Report 99-4259, 1999) and the calculation/handling of "simple" water-related tasks in daily routine practice. The software aqion is free for private users, education and companies.
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Fixation of alleles most likely occurs through Muller's ratchet, when an asexual population's genome accumulates deleterious mutations that are irreversible. Despite all its disadvantages, inbreeding can also have a variety of advantages, such as reducing the recombination load, and allowing the expression of recessive advantageous phenotypes. It has been proposed that under circumstances when the advantages of inbreeding outweigh the disadvantages, preferential breeding within small groups could be promoted, potentially leading to speciation.
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The value of the lab analysis has two aspects: cost and speciation. Smaller UPW facilities that cannot afford to purchase on-line instrumentation often choose off-line testing. TOC can be measured in the grab sample at a concentration as low as 5 ppb, using the same technique employed for the on-line analysis (see on-line method description). This detection level covers the majority of needs of less critical electronic and all pharmaceutical applications.
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The interglacial Sorata-Choqueyapu I may be contemporaneous to Lake Ballivián, as would be the Saale glaciation in Europe and the Illinoian glaciation in North America. During the Lake Ballivián episode, pupfish colonized the southern and central Altiplano. The diversification of Heleobia and Hyalella crustaceans, Orestias fish as well as the speciation of Biomphalaria snails may have also been influenced by the development of Lake Ballivián. The sponge Balliviaspongia is named after Lake Ballivián.
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Madame Berthe's mouse lemur (Microcebus berthae) or Berthe's mouse lemur is the smallest of the mouse lemurs and the smallest primate in the world; the average body length is and seasonal weight is around .Gron KJ. (11 February 2009). Primate Factsheets: Mouse lemur (Microcebus) Taxonomy, Morphology, & Ecology . Accessed 2009 August Microcebus berthae is one of many species of Malagasy lemurs that came about through extensive speciation, caused by unknown environmental mechanisms and conditions.
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The fall armyworm may be presently undergoing a divergence into two separate species. These two strains have major genetic differences that are connected to the plants they feed on, even though both still exist in the same area (sympatric speciation). These two strains can be loosely categorized into a rice strain and a corn strain. This separation is occurring because of differences in habitat (preferred host plant), and differences in reproductive behavior.
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Also, bidirectional cytoplasmic incompatibility occurs when an infected male carrying one strain of Wolbachia reproduces with an infected female carrying a different strain of Wolbachia. This also results in failed reproduction. Bidirectional cytoplasmic incompatibility also has evolutionary implications for populations of Ae. albopictus and other vectors of the infection. This is because bidirectional cytoplasmic incompatibility in Wolbachia creates unviable offspring, reducing gene flow between two populations, which can eventually lead to speciation.
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Other treatments after more than four episodes per year, may include ten days of either oral or topical treatment followed by fluconazole orally once per week for 6 months. About 10-15% of recurrent candidal vulvovaginitis cases are due to non-Candida albicans species. Non-albicans species tend to have higher levels of resistance to fluconazole. Therefore, recurrence or persistence of symptoms while on treatment indicates speciation and antifungal resistance tests to tailor antifungal treatment.
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2007, 48, 8242. Recent mechanistic studies have revealed a variety of protodeboronation pathways in aqueous media, and have demonstrated the reaction pH (and subsequently the boronic acid speciation) to be an important factor in understanding the modes of protodeboronation.Cox, P. A.; Leach, A. G.; Campbell, A. D.; Lloyd-Jones, G. C. "Protodeboronation of Heteroaromatic, Vinyl, and Cyclopropyl Boronic Acids: pH–Rate Profiles, Autocatalysis, and Disproportionation" J. Am. Chem. Soc. 2016, 138, 9145.
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Retrieved 10-23-2011. Davis' springparsley is a plant that is also endemic to the Albion Mountains. The South Hills crossbill is a bird believed to be a separate species than the Common crossbill, and it is endemic to the Albion Mountains and the South Hills due to ecological speciation. In February 1945 nine people died on Mount Harrison when a B-24 Liberator Army Bomber crashed during a training mission in dense fog.
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Sergey Gavrilets is a Russian-born American physicist turned theoretical biologist, and currently a Distinguished Professor at the University of Tennessee. He is a theoretical evolutionary biologist who has made contributions to the study of speciation, social complexity, and human evolutionary transitions. He is currently Associate Director for Scientific Activities at the National Institute for Mathematical and Biological Synthesis. In 2017, he was elected a Fellow of the American Academy of Arts and Sciences.
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The biodiversity of a lentic system increases with the surface area of the lake or pond. This is attributable to the higher likelihood of partly terrestrial species of finding a larger system. Also, because larger systems typically have larger populations, the chance of extinction is decreased. Additional factors, including temperature regime, pH, nutrient availability, habitat complexity, speciation rates, competition, and predation, have been linked to the number of species present within systems.
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With the exception of B. rosserae, no species tolerates annual rainfall of less than 200 millimetres, despite many species surviving in areas that receive less than 400 millimetres. Banksia species are present throughout the region of suitable rainfall, with greatest speciation in cooler, wetter areas. Hotter, drier regions around the edges of its range tend to have fewer species with larger distributions. The greatest species richness occurs in association with uplands, especially the Stirling Range.
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He is the author of the text Speciation and the bestselling non-fiction book Why Evolution Is True. Coyne maintains a website and writes for his blog, also called Why Evolution Is True. He is a hard determinist."You don't have free will", Vancouver, June 2015 Coyne gained attention outside of the scientific community when he publicly criticized religion and is often cited with atheists such as Richard Dawkins and Sam Harris.
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In such a case, pleiotropy would facilitate mating and survival. However, pleiotropy can act negatively as well. A study on seed beetles found that intralocus sexual conflict arises when selection for certain alleles of a gene that are beneficial for one sex causes expression of potentially harmful traits by the same gene in the other sex, especially if the gene is located on an autosomal chromosome. Pleiotropic genes act as an arbitrating force in speciation.
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In Michael Ruse (eds) The Cambridge Encyclopedia of Darwin and Evolutionary Thought, Cambridge University Press, Pp. 109–115. Similar claims were promulgated by the mutationist school of thought during the late 20th century, and even after the modern evolutionary synthesis by Richard Goldschmidt. Another strong proponent of this view about Darwin came from Mayr. Mayr maintained that Darwin was unable to address the problem of speciation, as he did not define species using the biological species concept.
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Individuals within the same environment can develop a preference for extremes of a trait, against the intermediate. Selection can act on having divergent body morphologies in accessing food, such as beak and dental structure. It is seen that often this is more prevalent in environments where there is not a wide clinal range of resources, causing heterozygote disadvantage or selection against the average. Niche partitioning allows for selection of differential patterns of resource usage, which can drive speciation.
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In all other tRNAs, this position is normally occupied by a pyrimidine (often uridine). This genetic code change is the only such known alteration in cytoplasmic mRNA, in both the prokaryotes, and the eukaryotes, involving the reassignment of a sense codon. This novel genetic code may be a mechanism for more rapid adaptation to the organism's environment, as well as playing an important role in the evolution of the genus Candida by creating genetic barriers that encouraged speciation.
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Erica Bree Rosenblum has published over 100 papers and has received over 3500 citations in total. She is known for her research on the fungus Batrachochytrium dendrobatidis that has caused high mortality rates and near extinction in some frog species. She is also known for her work in the evolution and speciation of lizards in White Sands, New Mexico . Rosenblum is often recognized for her effort to cause as little impact on the species she is researching as possible.
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Using these six concepts Pagenkopf looked at copper, zinc, cadmium, lead, combinations of metals, and hydrogen ion concentration using effective toxicant concentration. Per the results Pagenkopf assessed the applicability of the model and came up with several steps to using the GSIM. The required data are pH, alkalinity, hardness and total trace-metal content of a water sample. Once these parameters are obtained, the next step is to calculate the speciation of the metals in the water sample.
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Retrieved 2012-02-29. Fucus radicans and F. vesiculosus living together Fucus radicans seems to have diverged from the closely related and widely distributed Fucus vesiculosus within about the last 400 years. It often reproduces clonally, which may have helped its rapid emergence as a new species. Genetic analysis supports the hypothesis of the recent divergence of Fucus radicans from Fucus vesiculosus as an example of sympatric speciation, with the two species presently occupying the same semi-marine territory.
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The so-called cable bacteria are widespread in shallow marine sediments, and are believed to conduct electrons through structures inside a common periplasm of the multicellular filament, a process that may influence the cycling of elements at aquatic sediment surfaces, for instance, by altering iron speciation. The LSB and cable bacteria seem to be restricted to undisturbed sediment with stable hydrodynamic conditions, while symbiotic SOM and their hosts have been mainly found in permeable coastal sediments.
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The apple feeding race of this species appears to have spontaneously emerged from the hawthorn feeding race in the 1800–1850 AD time frame, after apples were first introduced into North America. The apple feeding race does not now normally feed on hawthorns, and the hawthorn feeding race does not now normally feed on apples. This may be an early step towards the emergence of a new species. Some parasitic ants may have evolved via sympatric speciation.
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Biogeography The Isthmus of Tehuantepec, a valley otherwise surrounded by montane habitats, has also been noted as an important biogeographical barrier among montane taxa, such as Mexican birds . Population diversification has been observed among, not only avian fauna, but other organisms as well, including toads and the Central American River Turtle. As a result, the Isthmus presents a case of allopatric speciation wherein a geographic divide gives rise to population divergence and a significant decrease in gene flow.
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The endemic fishes of Matano have been compared to the species swarms of the Rift Valley Lakes of Africa. While not as diverse, they are thought to have all arisen from a single ancestor species and diversified into numerous different species, which now fill many of the previously vacant ecological niches, as can be seen in the family Telmatherinidae.Herder, F., J. Pfaender, and U.K. Schliewen (2008). Adaptive sympatric speciation of polychromatic "roundfin" sailfin silverside fish in Lake Matano (Sulawesi).
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Iodide is not a pesticide, but is oxidized, by vegetable peroxidase, to iodine, which is a strong oxidant, able to kill bacteria, fungi and protozoa. The Cretaceous period saw the appearance of more plant defense mechanisms. The diversification of flowering plants (angiosperms) at that time is associated with the sudden burst of speciation in insects. This diversification of insects represented a major selective force in plant evolution, and led to selection of plants that had defensive adaptations.
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It has been suggested that, in some cases, the speciation process has taken place because of the incompatibility caused by this bacteria. Two wasp species Nasonia giraulti and N. longicornis carry two different strains of Wolbachia. Crosses between an infected population and one free from infection produces a nearly total reproductive isolation between the semi-species. However, if both species are free from the bacteria or both are treated with antibiotics there is no reproductive barrier.
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Organisms endemic to terra firme forest should be more affected than those that live in alluvial forests alongside the river, as they have a longer distance to cross before reaching appropriate habitat and lowland populations can rejoin relatively frequently when a river shifts or narrows in the early stages of oxbow lake formation. Finally, if a river barrier is the cause of speciation, sister species should exist on opposing shores more frequently than expected by chance.
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Okitsu, S., Sawaguchi, S., Hasegawa, H., Kanda, H., 2004, Vegetation development on the glacier moraines in Oobloyah Valley, Ellesmere Island, high arctic Canada, National Institute of Polar Research, Polar Biosci., 17, 83-94 It is also suggested that part of the high proportions of polypoids occurring in arctic floras is the result of speciation as continental ice-sheets withdrew.Bennett, K.D., 1988, Post- glacial vegetation history: ecological considerations, Kluwer Academic Publishers, Handbook of Vegetation science, vol.7, pp.
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There have been issues coming to a specific consensus about the taxonomy of the genus Difflugia. In 1988, an attempt to characterize and create a phylogenetic tree based upon the composition of the shell . However, with additional evidence it was found that this is not actually a useful characteristic to evaluate by. In addition, most initial descriptions of Difflugia speciation were completed using light microscopy and therefore lacked the technology to show the details of test structure and composition.
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A phylogenetic analysis using mtDNA of the entire group (including all species and subspecies of the Eumeces group inhabiting the western United States) combined with comparative approaches to morphology, and geographic distribution showed "instances of parallel morphological evolution...and provide evidence that this system is consistent with a model of ecological speciation" due to "the similarity in early ontogenetic trajectories and the close association between differences in body size and color pattern[s]" of each morphotype.
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Coquerel’s sifakas, like many lemurs, have been studied to help scientists learn about the evolutionary history of primates, including humans. Since they are so endangered and hunted in Madagascar, the ecotourism industry has benefited greatly because of the sifaka and brings people into the country. Scientists study the sifaka to get insight of evolution, and they have been the subject of those researching evolution of color vision, paternal care, matriarchal primate societies, and causes of speciation.
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The genus Allonautilus, which contains a mere 2 species, is a sister genus of the Nautilus which contains 11 species, 5 of which are widely accepted as being distinct. The Allonautilus is very understudied and not much is known about it. However, the more commonly known sister genus, the Nautilus, has been known to natural historians since the renaissance. Nautiluses show very little speciation within the genus and are a distant cousin to the squid and octopus.
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Phyletic gradualism, top, would consist of steady evolutionary change in small steps, in contrast to punctuated equilibrium Apparently sudden changes can be explained either by macromutation or by relatively rapid episodes of gradual evolution, since 10,000 years barely registers in the fossil record. Phyletic gradualism is a model of evolution which theorizes that most speciation is slow, uniform and gradual.Eldredge, N. and S. J. Gould (1972). "Punctuated equilibria: an alternative to phyletic gradualism" In T.J.M. Schopf, ed.
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Masatoshi Nei argues that evolution is often mutation-limited. In his 1940 book The Material Basis of Evolution, the German geneticist Richard Goldschmidt argued for single-step speciation by macromutation, describing the organisms thus produced as "hopeful monsters". Goldschmidt's thesis was universally rejected and widely ridiculed by biologists, who favoured the neo- Darwinian explanations of Fisher, J. B. S. Haldane and Sewall Wright. However, interest in Goldschmidt's ideas has reawakened in the field of evolutionary developmental biology.
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A map of Wallacea, bordered by the Wallace and the Lydekker Line. Although the distant ancestors of Wallacea's plants and animals may have been from Asia or Australia-New Guinea, Wallacea is home to many endemic species. There is extensive autochthonous speciation and proportionately large numbers of endemics; it is an important contributor to the overall mega-biodiversity of the Indonesian archipelago. Fauna species include the endemic anoa (dwarf buffalo) of Sulawesi and the babirusa (deer pig).
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Figure 6a: Morphologic change of Globorotalia crassaformis, G. tosaensis, and G. truncatulinoides over 3.5 Ma. Superimposed is a phylogenetic tree of the group. Adapted from Lazarus et al. (1995). Extensive research on the planktonic foraminifer Globorotalia truncatulinoides has provided insight into paleobiogeographical and paleoenvironmental studies alongside the relationship between the environment and evolution. In an extensive study of the paleobiogeography of G. truncatulinoides, researchers found evidence that suggested the formation of a new species (via the sympatric speciation framework).
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One example of evolution at work is the case of the hawthorn fly, Rhagoletis pomonella, also known as the apple maggot fly, which appears to be undergoing sympatric speciation. Different populations of hawthorn fly feed on different fruits. A distinct population emerged in North America in the 19th century some time after apples, a non-native species, were introduced. This apple- feeding population normally feeds only on apples and not on the historically preferred fruit of hawthorns.
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