Intraspecific variation in sperm precedence in the bruchid beetle Callosobruchus maculatus

Abstract. By examining potential sources of intraspecific variation in sperm precedence, the underlying mechanisms of sperm competition in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) were investigated. The extent of sperm precedence was not related to either copulatory behaviour or body size (male and female). The extent of sperm precedence increased during the egg‐laying period, suggesting that the stratification of sperm within the spermatheca is not the mechanism of sperm precedence. Direct removal of sperm from the female's reproductive tract was not observed. Four other mechanisms (not mutually exclusive) are proposed to account for last‐male sperm precedence in this species.