Sexual Selection and Speciation

Sexual selection has a reputation as a major cause of speciation, one of the most potent forces driving reproductive isolation. This reputation arises from observations that species differ most in traits involved with mating success and from successful models of sexual selection–driven speciation. But how well proven is the case? Models confirm that the process can occur, but is strongest in conjunction with ecological or niche specialization. Some models also show that strong sexual selection can act against speciation. Studies using the comparative method are equivocal and often inconclusive, but some phylogeographic studies are more convincing. Experimental evolution and genetic or genomic analyses are in their infancy, but look particularly promising for resolving the importance of sexual selection. The case for sexual selection is not as strongly supported as, for example, allopatric speciation. Sexual selection probably contributes most effectively alongside ecological selection or selection for species recognition than as a solitary process.