"Allopatric" refers to a situation where separate populations of organisms exist in different geographic areas and are unable to interbreed due to the physical barriers that separate them, such as mountains or rivers. Full definition
Speciation by vicariance is widely regarded as the most common form of speciation; and is the primary model of allopatric speciation. (myintimcity.com)
But the climate change still had a deep impact on anthropoid evolution, because habitat fragmentation and an increased level of allopatric speciation took place as a result. (sciencedaily.com)
Our data illustrate that fitness can decline quickly in nature when previously allopatric species interbreed. (rsbl.royalsocietypublishing.org)