Allopatric speciation Two models of allopatric speciation. Since then, several distinguishing features, such as the black belly and forelimbs have gradually evolved. Differentiation in the butterfly, Erebia epiphron in the European mountains.
Different colors designate different races or forms.
Note that these races evolved in geographical isolation, that is, in allopatry. Such species complexes are called ring species. Allopatric speciation in North American freshwater fish, called shiners. When two populations that were evolving in geographical isolation come in contact they may hybridize, but the gene flow can be very restricted depending on the degree of genetic differences. Accidental mistakes in oviposition site selection lead to the establishment of sympatric populations of this species that did not interbreed due to their high fidelity to their host plant.