Allopatric speciation
Allopatric speciation is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow. Its name comes from Ancient Greek ἄλλος (állos) 'other' and πατρίς (patrís) 'fatherland', and is also called geographic speciation, vicariant speciation, and its earlier name the dumbbell model.