This chapter discussed speciation by genetic divergence following geographic isolation, which is ...

Sympatric speciation is thought to be uncommon but almost certainly has occurred. In one general scenario, a form of isolation in place, or in sympatry, may occur if certain males or females begin (by drift, perhaps) to prefer different resourcessay, a special site for mating or laying eggs. If their mates follow in this imprinting process, the two preference populations may begin to experience reduced gene flow between them, which if maintained long enough may bring about a degree of genetic divergence that would be selectively reinforced should some of the individuals from the two populations ever hybridize.