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Topic: Peripatric speciation

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	Punctuated Equilibria
		This pattern includes the characteristically abrupt appearance of new species, the relative stability of morphology in widespread species, the distribution of transitional fossils when those are found, the apparent differences in morphology between ancestral and daughter species, and the pattern of extinction of species.
		Peripatric speciation states that a population of an ancestral species in a geographically peripheral part of the ancestral range is modified over time until even when the ancestral and daughter populations come into contact, there is reproductive isolation.
		The adaptations of newly speciated daughter populations are forever excluded from the ancestral population because of reproductive isolation (2 above).
	www.talkorigins.org /faqs/punc-eq.html (3019 words)

	Peripatric speciation - Wikipedia, the free encyclopedia
		Peripatric speciation is a form of speciation, the formation of new species through evolution.
		In this form, new species are formed in isolated peripheral populations; this is similar to allopatric speciation in that populations are isolated and prevented from exchanging genes.
		Peripatric speciation was originally proposed by Ernst Mayr, and is related to the concept of a Founder effect, since small populations often undergo bottlenecks.
	en.wikipedia.org /wiki/Peripatric_speciation (128 words)

	PERIPATRIC SPECIATION : Encyclopedia Entry
		Peripatric speciation is a form of speciation, the formation of new species through evolution.
		In this form, new species are formed in isolated peripheral populations; this is similar to allopatric speciation in that populations are isolated and prevented from exchanging genes.
		Peripatric speciation was originally proposed by Ernst Mayr, and is related to the founder effect, because small living populations may undergo selection bottlenecks.
	www.bibleocean.com /OmniDefinition/Peripatric_speciation (103 words)

	Ernst Mayr, "Speciational Evolution or Punctuated Equilibria," 1992
		On the contrary, the importance of peripatric speciation was minimized after Fisher (1930) and Wright (1931, 1932) had asserted, although for different reasons, that evolution was most rapid in populous, widespread species, a conclusion adopted also by Dobzhansky (1937, 1951) and by most evolutionists before the 1970s.
		That peripatric speciation is by far the most common mode of speciation is indicated not only by the pattern of distribution of incipient recent species but also by the frequency by which new species, apparently having originated somewhere else, suddenly appear in the fossil record.
		The evolutionary stability of large, widespread species is supported by the observation that most of the species in the fossil record that display stasis are large, widespread species with the samples taken from central populations.
	www.stephenjaygould.org /library/mayr_punctuated.html (10454 words)

	Peripatric speciation (Site not responding. Last check: 2007-10-26)
		Peripatric speciation is a form of speciation, the formation of new species through evolution.
		In this form, new species are formed in isolated peripheral populations.
		This is similar to allopatric speciation but with the distinction that these species stop changing after becoming self sustaining.
	www.xasa.com /wiki/en/wikipedia/p/pe/peripatric_speciation.html (67 words)

	Evolution II (Site not responding. Last check: 2007-10-26)
		Peripatric speciation (by evolution in an isolated colony) b.
		Vicariant speciation Speciation by reproductive isolation of populations that are divided by the emergence of an extrinsic barrier, or by the extinction of intervening populations, or by migration into geographically separated regions.
		Peripatric speciation (founder effect) Speciation by reproductive isolation of sub-populations peripheral to the main body of a population.
	eebweb.arizona.edu /Courses/Ecol435_535/Oct21.htm (914 words)

	Species and Speciation [MT Dorak]
		Speciation is thus seen in terms of the evolution of isolating mechanisms and is said to be complete when reproductive barriers are sufficient to prevent gene flow between the two new species.
		Speciation is generally described as multiplication of species by the division of one species into two or more separate species, thus leaves out the anagenetic speciation.
		When two species get together after a period of allopatric divergence (secondary contact): (1) they have already speciated and cannot interbreed; (2) their hybrids have lowered fitness and natural selection rapidly acts to develop reproductive isolation mechanisms; (3) they interbreed successfully and mix again as single species.
	www.dorak.info /evolution/species.html (2241 words)

	Qwika - similar:Ernst_Mayr
		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).
		However, peripatric speciation, unlike allopatric speciation, proposes that one of the populations is much smaller t...
		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.
	www.qwika.com /rels/Ernst_Mayr (1654 words)

	[No title]
		Species A gave rise to species B via the process of speciation and became extinct when species B invaded the range of species A. If this hypothesis is correct it would be predicted that both species A and species B should be found in the layer between the two original strata.
		Species A became extinct and then species B, which lived elsewhere, migrated to the locality sampled and so only appears to have evolved from species A. This hypothesis would predict that neither species should be found in the intermediary layer.
		Species selection as a process of differential extinction would seem to be reducible to the individual level - species survival is a function of individual survival.
	www.holycross.edu /departments/biology/whealy/notes_text/o.text (3069 words)

	Allopatric speciation - Wikipedia, the free encyclopedia (Site not responding. Last check: 2007-10-26)
		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).
		Proponents of peripatric speciation contend that small population size in the peripheral isolate allows genetic drift, which can be a more powerful force than natural selection in small populations, to deconstruct complex genotypes, allowing the creation of novel gene combinations.
	88.208.194.172 /wiki/index.php/Allopatric_speciation (283 words)

	Speciation: sympatric speciation, the speciation and biogeography of bird, definition of speciation (Site not responding. Last check: 2007-10-26)
		There are four modes of natural speciation, based on the extent to which speciating populations are geographically isolated from one another: allopatric, peripatric, parapatric, and sympatric.
		In peripatric speciation, new species are formed in isolated, small peripheral populations which are prevented from exchanging genes with the main population.
		New species have been created by domesticated animal husbandry, but the initial dates and methods of the initiation of such species are not clear.
	en.advantacell.com /wiki/Speciation (1552 words)

	Species and Speciation [MT Dorak]
		Speciation is thus seen in terms of the evolution of isolating mechanisms and is said to be complete when reproductive barriers are sufficient to prevent gene flow between the two new species.
		Speciation is generally described as multiplication of species by the division of one species into two or more separate species, thus leaves out the anagenetic speciation.
		The common factor in all mechanisms of speciation is a reduction in gene flow between two populations.
	dorakmt.tripod.com /evolution/species.html (2237 words)

	John Hawks Anthropology Weblog : Speciation (Site not responding. Last check: 2007-10-26)
		Speciation is the cessation of interbreeding between one animal population and all other populations with which it formerly exchanged genes.
		Each speciation is the birth of a new species, and species may disappear by extinction, when none of their members survive.
		Speciations and extinctions follow a different pattern than the births and deaths of individuals within a population, and although both speciations and extinctions are the result of evolution within populations, their pattern cannot necessarily be predicted from the forces of evolution alone.
	johnhawks.net /weblog/topics/phylogeny/speciation.html (3201 words)

	[No title] (Site not responding. Last check: 2007-10-26)
		Contingent to the species life history, "persistence requires that for a given extinction rate, the colonization rate exceeds a threshold value, and that for a given colonization rate the extinction rate is smaller than a threshold value."...
		There are five models of speciation: basic allopatry model of vicariant speciation, reinforcement model of allo-parapatric speciation, bottleneck model of peripatric speciation, and divergence-with-gene flow model of either parapatric or sympatric speciation.
		I couple bottleneck model and peripatric speciation because both processes have as initial condition a sudden circumstance in which the population size is extremely low, be it caused by drastic reduction of population size in the bottleneck model or by colonization by one or a very small number of founding dispersers.
	ib.berkeley.edu /courses/ib160/past_papers/vidigal-jones.html (3098 words)

	Allopatric speciation - EvoWiki
		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).
		Proponents of peripatric speciation contend that small population size in the peripheral isolate allows genetic drift, which can be a more powerful force than natural selection in small populations, to deconstruct complex genotypes, allowing the creation of novel gene combinations.
		Genetic models of peripatric speciation are similar to "peak shift" models of adaptation, such as Sewell Wright's shifting balance theory.
	wiki.cotch.net /index.php/Allopatric_speciation (302 words)

	Syllabus
		Peripatric speciation: separation of species when a small groups is separated allopatrically from the larger group.
		Vicariant speciation: also known as dumbbell allopatry, the mode of speciation in which there is geographic barrier between two larger groups of the same species.
		When two species have diverged sufficiently that they can mate without causing the overmixing and collapse of their own species, it can be advantageous for them to mate and create hybrid species.
	www.bio.davidson.edu /people/mastanback/evolution/Evol04Rev2KEY.htm (2650 words)

	The Panda's Thumb: Living Words: Pro patria - species and homeland security
		Speciation is also referred to as macroevolution, an increase in biodiversity, or as taxonomic multiplication.
		Species can thus be formed through random sampling "error", if the combined differences of otherwise fitness-neutral genes add up to sexual isolation when they get back together; that is, when they become sympatric again.
		Peripatric speciation is caused by being at the edge of the range and almost isolated geographically.
	www.pandasthumb.org /archives/2004/03/living_words_pr.html (2462 words)

	Wikinfo \| Punctuated equilibrium (Site not responding. Last check: 2007-10-26)
		This theory is one of the proposed explanations of the evolutionary patterns of species as observed in the fossil record, particularly the relatively sudden appearance of new species in a geologically short time period, and the perhaps typical lack of substantial change of species during their existence.
		Punctuated equilibria relies heavily on Ernst Mayr's concept of peripatric speciation and was articulated as a distinct theory by Niles Eldredge and Stephen Jay Gould in 1972.
		Due to the rarity of preservation and the likelihood that speciation occurs in small populations during geologically short periods of time, transitions between species are uncommon in the fossil record.
	www.wikinfo.org /wiki.php?title=Punctuated_equilibrium (1033 words)

	Peripatric speciation at AllExperts
		Peripatric speciation is a form of speciation, the formation of new species through evolution.
		In this form, new species are formed in isolated peripheral populations; this is similar to allopatric speciation in that populations are isolated and prevented from exchanging genes.
		Peripatric speciation was originally proposed by Ernst Mayr, and is related to the concept of a Founder effect, since small populations often undergo bottlenecks.
	en.allexperts.com /e/p/pe/peripatric_speciation.htm (216 words)

	Evolution - A-Z - Peripheral isolation
		In peripatric speciation a small population, at the extreme edge of the species' range, is separated off.
		Isolation: gene flow from the rest of the species may be reduced on the island, allowing the population there to diverge.
		The peripheral isolation model of speciation is the one favored by the theory of punctuated equilibrium.
	www.blackwellpublishing.com /ridley/a-z/Peripheral_isolation.asp (299 words)

	f29 Spatial or distributional elements in speciation
		Alternative hypotheses are that allopatric speciation occurred on a local scale within each lake; or that parallel invasions of the lakes by two species that originated in different lakes were followed by hybridization between the two and the spread of mitochondria from one species to the other.
		Parapatric speciation, which differs from sympatric speciation primarily in that the differentiating group, here more obviously a geographically definable deme, is marginal to the main body of the ancestral species.
		One is that, when related species reach clear distinction in different areas, as in (a) and (b) and to a lesser extent in (c), it is rarely possible to follow their exact courses in geologic time.
	geowords.com /histbooknetscape/f29.htm (1615 words)

	Allopatric speciation Summary
		The mode of speciation just described, involving genetic divergence of allopatric populations, is believed to explain the occurrence of different, but closely related species in remote oceanic archipelagos.
		All of these distinct, unusual species are thought to have evolved because their originally homogeneous, founder population was able to diverge genetically in the isolated environments of the various islands of the Galapagos Archipelago.
		In peripatric speciation, however, the genetic changes that are thought to occur within the peripheral isolate are more controversial.
	www.bookrags.com /Allopatric_speciation (924 words)

	Reference.com/Encyclopedia/Allopatric speciation
		Although there is some debate about the frequency of other types of speciation (such as sympatric speciation, parapatric speciation, and heteropatric speciation), all evolutionary biologists agree that allopatry is a common way that new species arise.
		In peripatric speciation, however, the genetic changes that are thought to occur within the peripheral isolate are more controversial.
		Proponents of peripatric speciation contend that small population size in the peripheral isolate (sometimes referred to as a "splinter population") allows genetic drift, which can be a more powerful force than natural selection in small populations, to deconstruct complex genotypes, allowing the creation of novel gene combinations.
	www.reference.com /browse/wiki/Vicariance (371 words)

	The Talk.Origins Archive Post of the Month: June 2006
		So allopatric speciation is "speciation that happens when the populations are isolated geographically".
		In this case a population of, say, flowering plants, is able to cross with some other species, but the progeny aren't thereby members of a new species, but backbreed into the population, changing its genetic constitution and adaptive niche so that when it is in sympatry with the original species, the population is now isolated.
		Speciation studies focus a lot on "reproductive isolating mechanisms" (RIMs) which are the particular mechanisms that keep populations from sharing their genes.
	www.talkorigins.org /origins/postmonth/jun06.html (853 words)

	Speciation and the Future of Human Evolution
		Speciation is the process by which a new species is formed from a single initial species.
		What he missed was the fact that all of the species gathered there at the watering hole were all from a common lineage; humans on earth having spread millennia ago, separated by distance, and subject to both direct germ-line manipulation and the environmental forces of the local planetary (or system) conditions.
		In parapatric speciation, the new species evolve from contiguous populations.
	www.human-evolution.org /genetic_human_speciation.php (2862 words)

	Models of Speciation (Site not responding. Last check: 2007-10-26)
		Speciation is a fundamental issue in evolutionary biology, but it is both fascinating and frustrating: we know it does happen but it its an historical phenomenon so it is difficult to observe.
		A variant of a species could be adapted to live in a particular environment that is spatially distinct from other types of environmental conditions; here an intrinsic component contributes to an extrinsic barrier.
		In this case speciation was not completed in allopatry and fate of the two populations depends on the outcome of the interaction upon secondary contact.
	biomed.brown.edu /Courses/BIO48/21.Models.HTML (1986 words)

	[No title]
		In allopatric speciation, populations of a species become isolated by a physical barrier and are unable to exchange genes by mating.
		Allopatric speciation is the consequence of independent evolution in geographically isolated populations.
		Peripatric speciation: A new species is formed when a small population migrates over a barrier and becomes isolated from the parental population.
	www.gwu.edu /~darwin/BiSc150/Species/species.html (1426 words)

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