The effects of copulation duration in the bruchid beetle Callosobruchus maculatus

摘要

Control over copulation duration is a potentially important generator of sexual conflict that has received little empirical attention. The copulatory behavior of the bruchid beetle Callosobruchus maculatus may reflect a sexual conflict over copulation duration. Males have spines on their intromittent organs that puncture the female reproductive tract, and females kick their mates during copulation. If females are prevented from kicking, copulations last longer and the injuries females sustain are more severe. Males supposedly use the spines as anchors to prolong copulation duration, and females kick to terminate copulations. We manipulated copulation duration experimentally and quantified its effects on male and female fitness components to test whether or not there is a conflict over copulation duration in C. maculatus. Females did not suffer from long copulations but instead experienced increased lifetime fecundity. Ejaculate size increased with copulation duration, and females apparently derive material benefits from the ejaculates. Males that mated first and had long copulations were relatively unsuccessful when competing with sperm from other males. However, there was a trend for female remating propensity to decrease with long copulation durations, and first males may therefore also benefit from long copulations. The copulation duration of the second male to mate did not have a significant effect on sperm precedence. We conclude that even though it seems likely that the male spines have evolved to act as an anchor during copulation, there seems to be little conflict over copulation duration per se in C. maculatus.