Peripatric and peripatry are terms from biogeography

Biogeography

Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...

, referring to organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur – for example a wide river or a mountain range. Such organisms are usually closely related (e.g. sister species), their distribution being the result of peripatric speciation.

Peripatric speciation is a form of speciation

Speciation

Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...

, the formation of new species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 through evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

. In this form, new species are formed in isolated peripheral populations; this is similar to allopatric speciation

Allopatric speciation

Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...

 in that populations are isolated and prevented from exchanging genes. However, peripatric speciation, unlike allopatric speciation, proposes that one of the populations is much smaller than the other. One possible consequence of peripatric speciation is that a geographically widespread ancestral species becomes paraphyletic, thereby becoming a paraspecies

Paraspecies

A paraspecies is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. The concept of a paraspecies emerges naturally from the Evolutionary Species Concept . Geographically widespread species that have given rise to one or more daughter...

. The concept of a paraspecies is therefore a logical consequence of the Evolutionary Species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 Concept, by which one species give rise to a daughter species. The evolution of the polar bear

Polar Bear

The polar bear is a bear native largely within the Arctic Circle encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest land carnivore and also the largest bear, together with the omnivorous Kodiak Bear, which is approximately the same size...

 from the brown bear

Brown Bear

The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

 is a well-documented example of a living species that gave rise to another living species through the evolution of a population located at the margin of the ancestral species' range.

Peripatric speciation was originally proposed by Ernst Mayr

Ernst Mayr

Ernst Walter Mayr was one of the 20th century's leading evolutionary biologists. He was also a renowned taxonomist, tropical explorer, ornithologist, historian of science, and naturalist...

, and is related to the founder effect

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, using existing theoretical work by those such as Sewall...

, because small living populations may undergo selection bottlenecks. Genetic drift

Genetic drift

Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...

is often proposed to play a significant role in peripatric speciation.