Sexual dimorphism in remating in Hawaiian Drosophila species

Abstract

Males and females have been predicted to show similar patterns of return to receptivity after mating, as a consequence of the genetic correlation between these traits in the two sexes. This hypothesis was tested by comparing mating and remating behaviour among several species of Hawaiian Drosophila. The species have diverged in their probability of first-time matings as well as in other aspects of their reproductive behaviour. Drosophila differens was monomorphic in remating behaviour. The two phylogenetically younger species, D. silvestris and D. heteroneura, both showed sexual dimorphism in remating behaviour, with males being equally likely to mate on 2 successive days and females being much less likely to mate on the first day after a copulation. Each species is sexually dimorphic in secondary sexual morphology, but the species differ in secondary sexual characters. With so few taxa, it is difficult to infer whether monomorphism or dimorphism is the ancestral condition. However, the existence of other dimorphisms that differ between species demonstrates that sufficient time has passed since population divergence to allow dimorphic behaviour to evolve independently in each species. Consequently, although we cannot rule out the hypothesis that males and females showed similar remating behaviour when each species was first formed, even in these very young species, sufficient time has passed for dimorphisms to evolve and for the effects of genetic correlations between the sexes to be rendered insignificant in maintaining monomorphisms.