peripatric

Peripatric is an adjective used in biology to describe processes occurring at the periphery of a population or range. In evolutionary biology, it is most often used in the context of peripatric speciation, a mode of speciation in which a small population becomes geographically isolated at the edge of a larger, ancestral population and diverges to form a new species.

Key elements include a founder event: a small number of individuals colonize a new, marginal habitat. The small size magnifies genetic drift and the founder effect, causing rapid genetic differentiation from the parent population. Selection in the new environment and reduced gene flow with the ancestral population can reinforce divergence. Over time, reproductive isolation—prezygotic or postzygotic barriers—may evolve, making successful interbreeding unlikely.

Peripatric speciation is often contrasted with allopatric speciation, where large, equally sized populations are separated; peripatric emphasizes peripheral, small populations. It is also discussed alongside parapatric and sympatric models as part of the spectrum of geographic speciation scenarios. Islands, isolated habitats, and fragmented landscapes provide common contexts for peripatric processes, where colonizing lineages can give rise to distinct island species.

Evidence for peripatric speciation includes phylogeographic patterns showing pronounced differentiation with limited contact zones, and observations of rapid divergence after colonization events. While not all peripheral divergence equals peripatric speciation, the model remains a useful framework for understanding how small founder populations contribute to the generation of biodiversity.