Inhibition of female mating receptivity by male-derived extracts in two Callosobruchus species: Consequences for interspecific mating

We investigated the effects of injecting male-derived extracts on congeneric female receptivity in two species of Callosobruchus beetle, C. chinensis and C. maculatus. We also examined the influence of interspecific mating on female remating behaviour in these two species. Male-derived extracts reduced congeneric female receptivity in both species. As quick-acting components, extracts of C. chinensis male seminal vesicles reduced the receptivity of C. maculatus females, whereas extracts of C. maculatus male testes reduced the receptivity of C. chinensis females. As slow-acting components, extracts of male accessory glands of other species reduced the receptivity of both C. maculatus and chinensis females. After interspecific mating, the sperm of C. maculatus males were transferred to the reproductive organs of C. chinensis females, thereby reducing their receptivity. In contrast, no C. chinensis sperm were transferred to the reproductive organs of C. maculatus females; accordingly, the latter's receptivity was not reduced. Furthermore, the survival rate of C. chinensis females decreased markedly after interspecific mating. These results raise the possibility that under circumstances where populations of these two species share the same habitat, reproductive interference would occur only in the interactions between C. maculatus males and C. chinensis females.