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Peripatric speciation is a mode of
speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...
in which a new
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
is formed from an isolated peripheral population. Since peripatric speciation resembles
allopatric speciation Allopatric speciation () – 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 ...
, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them, and peripatric speciation may be considered one type or
model A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , . Models can be divided in ...
of allopatric speciation. The primary distinguishing characteristic of peripatric speciation is that one of the populations is much smaller than the other, as opposed to (other types of) allopatric speciation, in which similarly-sized populations become separated. The terms peripatric and peripatry are often used in
biogeography Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...
, referring to
organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
s whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur—for example on an
oceanic island An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been ...
compared to the mainland. 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 Ernst Walter Mayr ( ; ; 5 July 1904 – 3 February 2005) was a German-American evolutionary biologist. He was also a renowned Taxonomy (biology), taxonomist, tropical explorer, ornithologist, Philosophy of biology, philosopher of biology, and ...
in 1954.Ernst Mayr. (1954). Change of genetic environment and evolution. In J. Huxley, A. C. Hardy & E. B. Ford. (eds) ''Evolution as a Process'', Unwin Brothers, London. Pp. 157–180. 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 Sexual selection is a mechanism of evolution in which members of one sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...
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. Scientists observing the patterns of a species biogeographic distribution and its
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
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 The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...
widely represented in much of the scientific literature.


History

Peripatric speciation was originally proposed by
Ernst Mayr Ernst Walter Mayr ( ; ; 5 July 1904 – 3 February 2005) was a German-American evolutionary biologist. He was also a renowned Taxonomy (biology), taxonomist, tropical explorer, ornithologist, Philosophy of biology, philosopher of biology, and ...
in 1954, and fully theoretically modeled in 1982. It is related to the
founder effect In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, us ...
, where small living populations may undergo selection bottlenecks. The founder effect is based on models that suggest peripatric speciation can occur by the interaction of selection and
genetic drift Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the Allele frequency, frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene va ...
, which may play a significant role. Mayr first conceived of the idea by his observations of
kingfisher Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly coloured birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species living in the tropical regions of Africa, Asia, and Oceania, ...
populations in New Guinea and its surrounding islands. '' Tanysiptera galatea'' was largely uniform in morphology on the mainland, but the populations on the surrounding islands differed significantly—referring to this pattern as "peripatric". This same pattern was observed by many of Mayr's contemporaries at the time such as by E. B. Ford's studies of '' Maniola jurtina''. 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 Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is depe ...
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 A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, wid ...
occurred. A small, isolated, founder population could be established on an island for example. 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. 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.


Models


Peripatric

Peripatric speciation models are identical to models of vicariance (allopatric speciation). Requiring both geographic separation and time, speciation can result as a predictable byproduct. Peripatry can be distinguished from allopatric speciation by three key features: *The size of the isolated population *Strong
selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strat ...
caused by the dispersal and colonization of novel environments, *The effects of
genetic drift Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the Allele frequency, frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene va ...
on small populations. The size of a population is important because individuals colonizing a new habitat likely contain only a small sample of the genetic variation of the original population. This promotes divergence due to strong selective pressures, leading to the rapid fixation of an
allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...
within the descendant population. This gives rise to the potential for genetic incompatibilities to evolve. These incompatibilities cause
reproductive isolation The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, ethology, behaviors and physiology, physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensu ...
, giving rise to—sometimes rapid—speciation events. Furthermore, two important predictions are invoked, namely that geological or climatic changes cause populations to become locally fragmented (or regionally when considering allopatric speciation), and that an isolated population's reproductive traits evolve enough as to prevent interbreeding upon potential secondary contact. The peripatric model results in, what have been called, progenitor-derivative species pairs, whereby the derivative species (the peripherally isolated population)—geographically and genetically isolated from the progenitor species—diverges. A specific
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
signature results from this mode of speciation: the geographically widespread progenitor species becomes
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
(thereby becoming a paraspecies), with respect to the derivative species (the peripheral isolate). The concept of a paraspecies is therefore a logical consequence of the evolutionary species concept, by which one species gives rise to a daughter species. It is thought that the character traits of the peripherally isolated species become apomorphic, while the central population remains
plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...
. Modern cladistic methods have developed definitions that have incidentally removed derivative species by defining clades in a way that assumes that when a speciation event occurs, the original species no longer exists, while two new species arise; this is not the case in peripatric speciation. Mayr warned against this, as it causes a species to lose their classification status. Loren H. Rieseberg and Luc Brouillet recognized the same dilemma in plant classification.


Quantum and budding speciation

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 Sewall Green Wright ForMemRS HonFRSE (December 21, 1889March 3, 1988) was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. He was a founder of population genetics alongside ...
(his models of genetic drift), Mayr (both his peripatric and genetic revolution models), and
George Gaylord Simpson George Gaylord Simpson (June 16, 1902 – October 6, 1984) was an American paleontologist. Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern synthesis, contributing '' Tempo ...
(his development of the idea of
quantum evolution Quantum evolution is a component of George Gaylord Simpson's multi-tempoed theory of evolution proposed to explain the rapid emergence of higher taxonomic groups in the fossil record. According to Simpson, evolutionary rates differ from group to ...
). 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. Inbreeding and genetic drift take 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. 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.


Centrifugal speciation

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. Because of the large size and potentially greater genetic variation within the central population,
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...
s arise more readily. These mutations are left in the isolated peripheral populations, 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. The phylogenetic signature of this model is that the central population becomes derived, while the peripheral isolates stay plesiomorphic—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. ''
Peromyscus ''Peromyscus'' is a genus of rodents. They are commonly referred to as deer mice or deermice, not to be confused with the chevrotain or "mouse deer". They are New World mice only distantly related to the common house and laboratory mouse, ''M ...
polionotus'' and ''P. melanotis'' (the peripherally isolated species from the central population of ''P. maniculatus'') arose via the centrifugal speciation model. Centrifugal speciation may have taken place in tree kangaroos, South American frogs ('' Ceratophrys''), shrews (''
Crocidura The genus ''Crocidura'' is one of nine genera of the shrew subfamily Crocidurinae. Members of the genus are commonly called white-toothed shrews or musk shrews, although both also apply to all of the species in the subfamily. With over 180 sp ...
''), and primates ('' Presbytis melalophos''). John C. Briggs associates centrifugal speciation with centers of origin, contending that the centrifugal model is better supported by the data, citing species patterns from the proposed 'center of origin' within the Indo-West Pacific


Kaneshiro model

The Kaneshiro Model also provides an explanation of the mechanism of speciation during founder events as proposed by Ernst Mayr and Hampton Carson. In most cases, founder events result when single fertilized female is accidentally translocated to an entirely different location, e.g., an adjacent island among a chain of islands such as the Hawaiian Archipelago, and produces a few offspring. Such a founder colony is faced with extremely small population size which as described by the Kaneshiro Model, experiences a shift in the mating system towards and increase in frequency of less choosy females. The resulting destabilization of the genetic system provides the milieu for new genetic variants to arise providing the recipe for speciation to occur. 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 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, while laboratory experiments are ongoing and yet to be completed in support of the model, there are field observations of shifts in the mating systems that undergo population bottlenecks which demonstrate that the dynamics of sexual selection is occurring in nature and therefore, it does represent a plausible process of peripatric speciation that takes place in nature.


Evidence

Observational evidence and laboratory experiments support the occurrence of peripatric speciation.
Island An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been ...
s and
archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...
s 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 Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
species on oceanic islands whose closest relatives inhabit a nearby
continent A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as ...
" must have originated by a colonization event. Comparative
phylogeography Phylogeography is the study of the historical processes that may be responsible for the past to present geographic distributions of genealogical lineages. This is accomplished by considering the geographic distribution of individuals in light of ge ...
of oceanic
archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Example archipelagos include the Aegean Islands (the o ...
s shows consistent patterns of sequential colonization and speciation along island chains, most notably on the
Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...
islands,
Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...
,
Society Islands The Society Islands ( , officially ; ) are an archipelago in the South Pacific Ocean that includes the major islands of Tahiti, Mo'orea, Moorea, Raiatea, Bora Bora and Huahine. Politically, they are part of French Polynesia, an overseas country ...
,
Marquesas Islands The Marquesas Islands ( ; or ' or ' ; Marquesan language, Marquesan: ' (North Marquesan language, North Marquesan) and ' (South Marquesan language, South Marquesan), both meaning "the land of men") are a group of volcano, volcanic islands in ...
,
Galápagos Islands The Galápagos Islands () are an archipelago of volcanic islands in the Eastern Pacific, located around the equator, west of the mainland of South America. They form the Galápagos Province of the Republic of Ecuador, with a population of sli ...
,
Austral Islands The Austral Islands ( officially ''Archipel des Australes;'' ) are the southernmost group of islands in French Polynesia, an overseas country of France, overseas country of the France, French Republic in the Oceania, South Pacific. Geographicall ...
, and the Hawaiian Islands—all of which express geological patterns of spatial isolation and, in some cases, linear arrangement. 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 ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...
'', for example, are separated from one another and evolve in reproductive isolation.


Hawaiian archipelago

''
Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...
'' 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). Studies consistently find that colonization of each island occurred from older to younger islands, and in ''Drosophila'', speciating peripatrically at least fifty percent of the time. In conjunction with ''Drosophila'', Hawaiian lobeliads ('' Cyanea'') have also undergone an adaptive radiation, with upwards of twenty-seven percent of
extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...
species arising after new island colonization—exemplifying peripatric speciation—once again, occurring in the old-to-young island direction. 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". 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, Numerous arthropods have been documented existing in patterns consistent with the geologic evolution of the island chain, in such that, phylogenetic reconstructions find younger species inhabiting the geologically younger islands and older species inhabiting the older islands (or in some cases, ancestors date back to when islands currently below sea level were exposed). Spiders such as those from the genus '' Orsonwelles'' exhibit patterns compatible with the old-to-young geology. Other endemic genera such as ''
Argyrodes The genus name is a combination of the Ancient Greek " argyros" (), meaning "silver", and the suffix "-odes", meaning "like". ''Argyrodes'', also called dewdrop spiders, is a genus of comb-footed spiders that was first described by Eugène Louis ...
'' have been shown to have speciated along the island chain. '' Pagiopalus'', '' Pedinopistha'', and part of the family
Thomisidae The Thomisidae are a family of spiders, including about 170 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but is also applied loosely to many other families of spiders. Many members of thi ...
have adaptively radiated along the island chain, as well as the wolf spider family,
Lycosidae Wolf spiders are members of the Family (biology), family Lycosidae (), named for their robust and agile hunting skills and excellent eyesight. They live mostly in solitude, hunt alone, and usually do not spin spider web, webs. Some are opportunis ...
. A host of other Hawaiian endemic arthropod species and genera have had their speciation and phylogeographical patterns studied: the '' Drosophila grimshawi'' species complex,
damselflies Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies (which constitute the other odonatan suborder, Epiprocta) but are usually smaller and have slimmer bodies. Most species fold the win ...
('' 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 Insects in the family (biology), family Tettigoniidae are commonly called katydids (especially in North America) or bush crickets. They have previously been known as "long-horned grasshoppers". More than 8,000 species are known. Part of the subo ...
), '' Caconemobius'', '' Eupethicea'', '' Ptycta'', '' Megalagrion'', '' Prognathogryllus'', '' Nesosydne'', '' Cephalops'', '' Trupanea'', and the tribe Platynini—all suggesting repeated radiations among the islands.


Other islands

Phylogenetic studies of a species of crab spider ('' Misumenops rapaensis'') in the genus
Thomisidae The Thomisidae are a family of spiders, including about 170 genera and over 2,100 species. The common name crab spider is often linked to species in this family, but is also applied loosely to many other families of spiders. Many members of thi ...
located on the
Austral Islands The Austral Islands ( officially ''Archipel des Australes;'' ) are the southernmost group of islands in French Polynesia, an overseas country of France, overseas country of the France, French Republic in the Oceania, South Pacific. Geographicall ...
have established the, "sequential colonization of helineage down the Austral archipelago toward younger islands". ''M. rapaensis'' has been traditionally thought of as a single species; whereas this particular study found distinct genetic differences corresponding to the sequential age of the islands. The figwart plant species ''Scrophularia lowei'' is thought to have arisen through a peripatric speciation event, with the more widespread mainland species, ''Scrophularia arguta'' dispersing to the
Macaronesia Macaronesia (; ) is a collection of four volcanic archipelagos in the Atlantic Ocean#North Atlantic, North Atlantic Ocean, off the coast of North Africa and Europe. Each archipelago is made up of a number of list of islands in the Atlantic Oc ...
n islands. Other members of the same genus have also arisen by single colonization events between the islands.


Species patterns on continents

The occurrence of peripatry on continents is more difficult to detect due to the possibility of vicariant explanations being equally likely. However, studies concerning the Californian plant species '' Clarkia biloba'' and ''C. lingulata'' strongly suggest a peripatric origin. In addition, a great deal of research has been conducted on several species of land snails involving
chirality Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable fro ...
that suggests peripatry (with some authors noting other possible interpretations). The chestnut-tailed antbird (''Sciaphylax hemimelaena'') is located within the Noel Kempff Mercado National Park (Serrania de Huanchaca) in Bolivia. 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 The Tyranni (suboscines) are a suborder of passerine birds that includes more than 1,000 species, a large majority of which are South American. It is named after the type genus '' Tyrannus''. These have a different anatomy of the syrinx musculat ...
in Amazonia". The montane spiny throated reed frog
species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
(genus: '' Hyperolius'') originated through occurrences of peripatric speciation events. 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 ''Picea mariana'', the black spruce, is a North American species of spruce tree in the Pinaceae, pine family. It is widespread across Canada, found in all 10 provinces and all 3 Canadian Arctic Lands, territories. It is the official tree of Newfo ...
''). During the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
, a population of black spruce became geographically isolated, likely due to
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...
. The geographic range of the black spruce is much larger than the red spruce. The red spruce has significantly lower genetic diversity in both its DNA and its
mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...
than the black spruce. Furthermore, the genetic variation of the red spruce has no unique mitochondrial
haplotype A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material (DNA) which is inherited from two parents. Normally these organisms have their DNA orga ...
s, only subsets of those in the black spruce; suggesting that the red spruce speciated peripatrically from the black spruce population. It is thought that the entire genus ''
Picea A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Northern hemisphere. ''Picea'' is the sole genus ...
'' in North America has diversified by the process of peripatric speciation, as numerous pairs of closely related species in the genus have smaller southern population ranges; and those with overlapping ranges often exhibit weak reproductive isolation. Using a phylogeographic approach paired with ecological niche models (''i.e.'' prediction and identification of expansion and contraction species ranges into suitable habitats based on current
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...
s, correlated with fossil and molecular data), researchers found that the
prairie dog Prairie dogs (genus ''Cynomys'') are herbivorous burrowing Marmotini, ground squirrels native to the grasslands of North America. There are five recognized species of prairie dog: black-tailed prairie dog, black-tailed, white-tailed prairie dog ...
species '' Cynomys mexicanus'' speciated peripatrically from '' Cynomys ludovicianus'' approximately 230,000 years ago. North American glacial cycles promoted range expansion and contraction of the prairie dogs, leading to the isolation of a relic population in a refugium located in the present day
Coahuila Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 31 states of Mexico. The largest city and State Capital is the city of Saltillo; the second largest is Torreón and the thi ...
, Mexico. This distribution and paleobiogeographic pattern correlates with other species expressing similar biographic range patterns such as with the '' Sorex cinereus'' complex.


Laboratory experiments

Peripatric speciation has been researched in both laboratory studies and nature. Jerry Coyne and H. Allen Orr in ''Speciation'' suggest that most laboratory studies of allopatric speciation are also examples of peripatric speciation due to their small population sizes and the inevitable divergent selection that they undergo. Much of the laboratory research concerning peripatry is inextricably linked to
founder effect In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, us ...
research. Coyne and Orr conclude that selection's role in speciation is well established, whereas
genetic drift Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the Allele frequency, frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene va ...
's role is unsupported by experimental and field data—suggesting that founder-effect speciation does not occur. Nevertheless, a great deal of research has been conducted on the matter, and one study conducted involving
bottleneck Bottleneck may refer to: * the narrowed portion (neck) of a bottle Science and technology * Bottleneck (engineering), where the performance of an entire system is limited by a single component * Bottleneck (network), in a communication network * ...
populations of ''
Drosophila pseudoobscura ''Drosophila pseudoobscura'' is a species of Drosophilidae, 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 ...
'' found evidence of isolation after a single bottleneck. The table is a non-exhaustive table of laboratory experiments focused explicitly on peripatric speciation. Most of the studies also conducted experiments on vicariant speciation as well. The "replicates" column signifies the number of lines used in the experiment—that is, how many independent populations were used (not the population size or the number of generations performed).


References

{{DEFAULTSORT:Peripatric Speciation Biogeography Ecology Evolutionary biology Speciation