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	Speciation - Wikipedia, the free encyclopedia
		There are three main ideas concerning the emergence of new species (Modes of Speciation), each based on the degree to which populations undergoing this process are geographically isolated from one another (allopatric speciation, sympatric speciation, parapatric speciation).
		During allopatric speciation, a population splits into two geographically isolated allopatric populations (for example, by habitat fragmentation or emigration).
		New species have been created by domesticated animal husbandry, but the initial dates and exact methods of the initiation of such species are not clear.
	en.wikipedia.org /wiki/Speciation (718 words)

	Allopatric speciation - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-22)
		Allopatric speciation, also known as geographic speciation, occurs when populations physically isolated by an extrinsic barrier evolve intrinsic (genetic) reproductive isolation such that if the barrier between the populations breaks down, individuals of the two populations can no longer interbreed.
		Ernst Mayr, an evolutionary biologist and famous proponent of allopatric speciation, hypothesized that adaptive genetic changes that accumulate between allopatric populations cause negative epistasis in hybrids, resulting in sterility or inviability.
		Allopatric speciation may occur when a species is subdivided into two large populations (vicariant or dichopatric speciation) or when a small number of individuals colonize a novel habitat on the periphery of a species' geographic range (peripatric speciation).
	en.wikipedia.org /wiki/Allopatric_speciation (301 words)

	Geographical/Allopatric Speciation (October 2002) (Site not responding. Last check: 2007-10-22)
		Evolution and speciation of cave-dwelling Fulgoroidea in the Canary Islands (Homoptera: Cixiidae and Meenoplidae).
		Knowles, L. Genealogical portraits of speciation in montane grasshoppers (genus Melanoplus) from the sky islands of the Rocky Mountains.
		Restricted gene flow and incipient speciation in disjunct Pacific Ocean and Sea of Cortez populations of a reef fish species, Girella nigricans.
	www.eeb.uconn.edu /Courses/EEB449/449_allopatric.htm (2249 words)

	Speciation (Site not responding. Last check: 2007-10-22)
		Allopatric Speciation: the Role of Isolation in Speciation
		Although hybridization between related species of angiosperm also causes reduced fertility, it is sometimes followed by a doubling of the chromosome number.
		These benthic and limnetic species even display their mating preferences when presented with sticklebacks from Japanese lakes; that is, a Canadian benthic prefers a Japanese benthic over its close limnetic cousin from its own lake.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/S/Speciation.html (2381 words)

	Speciation - Wikibooks, collection of open-content textbooks
		The biological species concept, which was first introduced by Ernst Mayr, defines a species as a population whose members have the potential to interbreed to produce viable, fertile offspring, but do not produce healthy offspring with other species.
		Ring Species: A species distributed around some geographic barrier, with the populations that have diverged the most in their evolution eventually meeting where the ring closes.
		This example of allopatric speciation usually occurs when there are new areas for a species to occupy, after mass extinctions, or when natives have not colonized an area.
	en.wikibooks.org /wiki/Speciation (1380 words)

	Allopatric vs
		This is fundamentally different from allopatric speciation, where mutation passively leads to differences that allow divergence of the populations.
		Although there is evidence of allopatric speciation in natural populations, some aspects of the mechanism make it unlikely to be a powerful mechanism of speciation.
		This species has recently diverged into two subspecies due to the introduction of apple trees in the northeastern United States, where hawthorn trees were native.
	www.evotutor.org /Author/Research/Paper-EG2-Speciation.htm (983 words)

	Levels of Selection, and Speciation Mechanisms, Barry Sinervo
		One species or both species refuse to engage in the mating rituals because the stereotyped mating rituals are to different.
		In this case, the two species were in allopatry in the remote past and brought into secondary contact and weak gene flow began once the sibling species were rejoined at the hybrid zone.
		The formation of new sexual species by changes in ploidy and the formation of asexual species are both examples in which the new species becomes reproductively isolated from the parent.
	bio.research.ucsc.edu /~barrylab/classes/animal_behavior/SPECIATE.HTM (6803 words)

	Evolution - Speciation (Site not responding. Last check: 2007-10-22)
		Allopatric speciation occurs when a new species evolves in geographic isolation from its ancestor.
		The process of allopatric speciation is illustrated in the following animation.
		(b) The peripheral isolate model, in which the new species forms from a population isolated at the edge of the ancestral species range.
	www.blackwellpublishing.com /ridley/tutorials/Speciation5.asp (200 words)

	Lect_12.html
		Allopatric speciation refers to the case in which two populations become reproductively isolated as a consequence of independent evolution in allopatry.
		Parts of the genome from the two species can be followed through the crosses through use of either visible mutations (e.g., eye color mutants) or through the use of molecular markers that distinguish the two species' genomes.
		These species are typical in that when there is partial reproductive isolation between two species, it is almost always the heterogametic sex that is sterile or inviable.
	trc.ucdavis.edu /djbegun/Lect.13-15.04.html (4006 words)

	Allopatric Speciation of the Nile Tilapia (Site not responding. Last check: 2007-10-22)
		Perhaps the most spectacularly rapid and extensive speciation events are those that produced approximately 1000 species of cichlid fishes in the East African Lakes over the last 10 million years.
		The Cichlidae family fits into the model of allopatric (or geographic) speciation which was first proposed by Gould and Eldredge in 1972.
		Allopatric speciation states that a new species can arise when small, peripheral populations, on the edge of the species range, are separated.
	geology.fullerton.edu /faculty/dck/Geol303B/Mike_web/Mike_Barrier.htm (446 words)

	Introduction to Evolutionary Biology
		Both humans and living apes are fully modern species; the ancestor we evolved from was an ape, but it is now extinct and was not the same as present day apes (or humans for that matter).
		Allopatric speciation is thought to be the most common form of speciation.
		A species can be competitively excluded by a closely related species, the habitat a species lives in can disappear and/or the organisms that the species exploits could come up with an unbeatable defense.
	www.talkorigins.org /faqs/faq-intro-to-biology.html (15764 words)

	Untitled Document
		Allopatric speciation has long been recognized as a principle mechanism of speciation, but is most forcefully championed in the writings of Ernst Mayr (e.g.
		Allopatric speciation may proceed through random genetic change in isolated populations (indirectly through genetic drift) or it may proceed via genetic changes as a result of selection in contrasting environments (drift and selection may also interact to promote speciation in allopatry).
		First, sympatric speciation (or at least the absence of large scale allopatric speciation) is often suggested when the two species have completely overlapping ranges or when one species has a geographic range contained completely within the larger range of the other species.
	www.zoology.ubc.ca /~etaylor/413www/speciation2.html (3556 words)

	Speciation
		In such species, both mates compete intensively for scarce resources (e.g., nesting cavities for toucans and burrows for puffins) as well as for access to the best mates of the opposite sex (both sexes compete for mates and both parents invest heavily in parental care).
		Speciation here was probably NOT ecological -- the two sister species (horned and Atlantic) have different breeding microhabitats (rock crevices and earth burrows respectively), whereas the two most different species (Atlantic and tufted) are both burrowers.
		Perhaps the two major contenders at this point are Mayr (1942) and Dobzhansky’s (1937) biological species concept (BSC) based on the primacy of interbreeding as a criterion, versus the phylogenetic species concept (PSC) in which the major criterion is that species must be monophyletic units with a diagnosable shared character (synapopmorphy).
	www.uwyo.edu /dbmcd/molmark/lect2a.html (2986 words)

	Some More Observed Speciation Events
		Allopatric evolution occurs among geographically isolated populations, whereas sympatric evolution occurs within one species' entire population.
		Barton, N.H. Hewitt, G.M. Adaptation, speciation and hybrid zones; many species are divided into a mosaic of genetically distinct populations, separated by narrow zones of hybridization.
		Genus Rattus currently consists of 137 species [1,2] and is known to have originally developed in Indonesia and Malaysia during and prior to the Middle Ages [3].
	www.talkorigins.org /faqs/speciation.html (1472 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		Mechanisms of speciation Distinguish between the definitions of allopatric and sympatric populations.
		Explain this assertion by describing an example of a geographic feature that creates a barrier that could promote allopatric speciation for one kind of organism but would not be a barrier for another kind of organism.
		The section about allopatric speciation in your textbook may also be helpful in answering this question.) Define and distinguish between prezygotic and postzygotic reproductive barriers.
	www.hamline.edu /~bjploger/biocon1/biocon1lec/lec34 (657 words)

	"Species, Speciation, and the Environment" by Niles Eldredge, Ph.D.
		Species are reproductive communities, with their members capable of interbreeding among themselves, and not, as the general rule, with members of other species.
		Evolution of new species centers on how changes occur in adaptations so that an ancestral species is split into two (occasionally more) descendant species, with interbreeding no longer possible between the members of what have evolved into descendant, or "daughter," species.
		Species also remain stable because of the very nature of their internal structural organization; all species are broken up into local populations that are integrated into local ecosystems.
	www.actionbioscience.org /evolution/eldredge.html (3160 words)

	Allopatric speciation: the great divide
		Allopatric speciation is just a fancy name for speciation by geographic isolation, discussed earlier.
		Allopatric speciation can occur even if the barrier is a little "porous," that is, even if a few individuals can cross the barrier to mate with members of the other group.
		In order for a speciation even to be considered "allopatric," gene flow between the soon-to-be species must be greatly reduced — but it doesn't have to be reduced completely to zero.
	evolution.berkeley.edu /evolibrary/article/0_0_0/speciationmodes_02 (132 words)

	Speciation.S318
		Selection can promote speciation because genetic changes can rapidly accumulate in one area where selection favors certain behaviors, physiology, or morphology relative to another area where alternative alleles are favored by natural selection.
		Founder effect speciation is an extreme form of subdivision in species formation takes place in a small isolated population.
		Ring Species are a peculiar form of speciation that takes place when the center of a species range is effectively unoccupied and thus there is no gene flow.
	bio.research.ucsc.edu /~barrylab/classes/evolution/SPECIES.HTM (2335 words)

	Evolution: Library: Allopatric Speciation
		Nancy Knowlton of the Smithsonian Tropical Research Institute has been studying how this geological phenomenon produced a speciation event: Populations of snapping shrimp divided by the Isthmus have diverged into separate species.
		The biological equivalent is "allopatric speciation," an evolutionary process in which one species divides into two because the original homogenous population has become separated and both groups diverge from each other.
		In their separate niches, the two groups go their own evolutionary ways, accumulating different gene mutations, being subjected to different selective pressures, experiencing different historical events, finally becoming incapable of interbreeding should they ever come together again.
	www.pbs.org /wgbh/evolution/library/05/2/l_052_03.html (431 words)

	"Speciation" (Site not responding. Last check: 2007-10-22)
		In cladogenesis, a new species arises from a small population of the ancestral species.
		Mengel discussed speciation in the fl-throated green warbler group which includes one species in the eastern U.S., Dendroica virens, and three species in the western U.S. Mengel argued that a glaciation during the Pleistocene separated a species into eastern and western populations and that each differentiated from the original species.
		Although allopatric speciation might be the rule in many systems, the case of the evolution of insect species which specialize in a relationship with particular plants might be a situation where sympatric speciation is in operation.
	www.bio.miami.edu /tom/bil160/bil160goods/05_speciation.html (1088 words)

	Evolution at NYU--Speciation
		Exceptions suggest that speciation is a process that occurs by the gradual evolution of barriers to gene flow
		Speciation by divergence—isolation is a secondary consequence of genetic divergence between already separated populations
		Speciation by peak shifts—gene pools separated as a consequence of the dynamics between gene frequencies of subpopulations and natural selection, such as might be triggered by splinter groups ("founders")
	www.nyu.edu /projects/fitch/courses/evolution/html/speciation.html (381 words)

	BIO 304. Ecology & Evolution: Macroevolution
		Accidental mistakes in oviposition site selection lead to the establishment of sympatric populations of this species that did not interbreed due to their high fidelity to their host plant.
		The latter species was regarded as a variant of the former for long.
		In the group of the Hawaiian silverswords (plants in the sunflower family), one founding species gave rise to several, phenotypically very different species that not only look different, but also occupy very different habitats.
	www.micro.utexas.edu /courses/levin/bio304/evolution/speciation.html (498 words)

	Teachers' Domain: Allopatric Speciation
		The images depict research results by Nancy Knowlton of the Smithsonian Tropical Research Institute who has been studying how this geological phenomenon produced a speciation event: Populations of snapping shrimp divided by the isthmus have diverged into separate species.
		Often this type of speciation occurs in three steps.
		They had become separate species, just as the theory would predict.
	www.teachersdomain.org /9-12/sci/life/evo/allopatric/index.html (633 words)

	ALLOPATRIC SPECIATION (Site not responding. Last check: 2007-10-22)
		Speciation is allopatric if the newly _______ species occupy physically ___________ sites
		This may occur because each species is _____________ to different environments (which includes weather, disease, predators, etc)
		May also occur because of _________ _________ and the two species may ____________ ________ _________ that ___________ (breeding between species or populations) is no longer possible even if the two species come back into contact
	www.auburn.edu /academic/classes/biol/1000/speciation/sld008.htm (115 words)

	Reinforcement drives rapid allopatric speciation : Nature (Site not responding. Last check: 2007-10-22)
		Allopatric speciation results from geographic isolation between populations.
		We show that reinforcing natural selection has resulted in significant premating isolation of a population in the contact zone not only from the other lineage but also, incidentally, from the closely related main range of its own lineage.
		Thus we show the potential for reinforcement to drive rapid allopatric speciation.
	www.nature.com /nature/journal/v437/n7063/abs/nature04004.html (278 words)

	Allopatric speciation - EvoWiki
		Theory of Evolution > Speciation > Allopatric Speciation
		Genetic models of peripatric speciation are similar to "peak shift" models of adaptation, such as Sewell Wright's shifting balance theory.
		This page was last modified 09:18, 24 February 2006.
	wiki.cotch.net /index.php/Allopatric_speciation (302 words)

	Activity 23.2 Allopatric Speciation (Site not responding. Last check: 2007-10-22)
		Home > Speciation > Activities > Activity 23.2 Allopatric Speciation
		In this activity you’ll see examples of allopatric speciation, in which parts of a population become geographically isolated and subsequently evolve into different species.
		When the populations are isolated, forces of evolution, such as genetic drift, natural selection, and sexual selection cause them to diverge.
	wps.prenhall.com /esm_freeman_biosci_1/0,6452,499633-,00.html (122 words)

	Raving Media: October 2004 (Site not responding. Last check: 2007-10-22)
		Homo floresiensis ("Man of Flores") is a species of the genus Homo which is believed to have lived at the same time as modern humans.
		Flores has been described (by Nature magazine) as "a kind of Lost World", where archaic animals, which elsewhere had long become extinct, had evolved into giant and dwarf forms through allopatric speciation.
		The discoverers have informally referred to the dimunitive species as a "hobbit", after J.R.R. Tolkien's fictional race of roughly the same height.
	www.ravingmedia.info /2004_10_01_archive.php (1783 words)

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