allopatric

Describing a population or species that is unable to breed with a related group of organisms because of geographical separation by distance or by natural barriers, such as water, mountain ranges, deserts, etc. If two groups that have been separated in such a way develop different adaptations such that they would not be able to interbreed even if the barriers broke down then allopatric speciation is said to have occurred. Compare sympatric . See also vicariance .