Mating preference evolution has sex-opposite effects on species persistence under reproductive interference

Abstract

Reproductive interference, where interspecific mating activities have negative effects on reproductive output, can impact the expansion of one species’ range into that of a related competitor. Theory to date suggests that if species recognition mechanisms evolve rapidly enough, the attenuation of reproductive interference may allow range expansions to proceed (a form of evolutionary rescue). Here, we show that sex differences cause evolvability not to have a uniformly positive effect on population fitness at the range front, nor on coexistence. We allow mate choice to evolve in males, where it takes the form of a courtship bias towards conspecific females, and/or in females, where a receptivity bias favours conspecific males. The beneficial effect of rapid evolution is highly contingent on (1) the asymmetry in the evolvability of mate preference between the two species and (2) the sex that controls the outcome of mating interactions. When female preferences dictate mating outcomes, rapid evolution increases the likelihood of range expansion by the fast evolving species, the other species being outcompeted. In contrast, rapid evolution of male mate choice has a detrimental effect on persistence in the zone of potential coexistence. We also show that if both sexes evolve their preferences, the female effect tends to override the male effect, and evolvability’s net effect on population fitness remains positive. Thus, while rapid evolution of traits related to reproductive interference likely aid range expansion, case by case inference requires knowledge of the mating systems in question.