Female modulation of reproductive rate and its role in postmating prezygotic isolation in Callosobruchus maculatus

Abstract

Summary Mechanisms that come into play after mating but prior to fertilization can prevent hybrid formation and thus promote reproductive isolation. Recent research indicates that the evolution of such barriers to gene exchange between incipient forms appears to be common and is essential for speciation. We aimed to test if female Bean Weevils (Callosobruchus maculatus) modulate their reproductive rate and/or remating propensity in response to mating with males with varying degrees of relatedness in a manner that limits the number of ‘hybrids’ produced. We also tested if remating with a male from a female's own population, following a first mating with a foreign male, would elevate egg production. Females varied their egg‐production rate depending on the relatedness of their mates, but this effect was not in the predicted direction. Heterospecific C. analis males actually elicited the strongest reproductive response in females, which resulted in up to 9% higher egg production. Male relatedness did not significantly affect female propensity to remate with a second male. Further, females did not generally show a compensatory increase in reproductive rate following rematings with males from their own population. The mechanisms documented here do not act to limit gene flow and are costly to females, as they suffer reduced life span and egg production late in life following a high reproductive rate early in life. We suggest that sexually antagonistic coevolution within species may have caused the pattern observed.