Allopatric

Definition

Occurring in separate, non-overlapping geographic areas; describes populations or species whose ranges are isolated by physical or ecological barriers that prevent or severely limit gene flow. In arthropod systematics, allopatric distributions are distinguished from sympatric (overlapping) and parapatric (adjacent) patterns, and often provide the geographic context for allopatric speciation.

Etymology

From Greek allos (other, different) + patra (fatherland, native country)

Example

The weevil Trigonopterus allopatricus and its sister species occupy isolated mountain ranges in New Guinea, with populations separated by lowland barriers that prevent dispersal and maintain reproductive isolation.

Synonyms

• geographically isolated
• vicariant

Related Terms

• sympatric
• parapatric
• vicariance
• Allopatric speciation
• disjunct distribution
• biogeographic barrier

Usage Notes

Contrasts with sympatric (same area, potentially interbreeding) and parapatric (abutting ranges with limited contact). Often used to describe both the spatial pattern and the evolutionary process it may facilitate. Not all allopatric populations undergo speciation; the term describes geography, not evolutionary outcome. In practice, biologists assess allopatry by range maps and genetic differentiation, recognizing that cryptic sympatry (microhabitat separation) can mimic geographic isolation.