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. 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.
Hawaiian archipelago 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). 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. 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
ʻElepaio 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 have been shown to have speciated along the island chain.
Pagiopalus,
Pedinopistha, and part of the family
Thomisidae have adaptively radiated along the island chain, as well as the wolf spider family,
Lycosidae. 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.
Other islands Phylogenetic studies of a species of crab spider (
Misumenops rapaensis) in the genus
Thomisidae located on the
Austral Islands have established the, "sequential colonization of [the] lineage 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
Macaronesian 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. In addition, a great deal of research has been conducted on several species of land snails involving
chirality that suggests peripatry (with some authors noting other possible interpretations). Red spruce (
Picea rubens) has arisen from an isolated population of black spruce (
Picea mariana). During the
Pleistocene, a population of black spruce became geographically isolated, likely due to
glaciation. 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 than the black spruce. Furthermore, the genetic variation of the red spruce has no unique mitochondrial
haplotypes, 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 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. This distribution and
paleobiogeographic pattern correlates with other species expressing similar biographic range patterns
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. 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 ==