Male age, mating probability and mating costs in the fly Sepsis cynipsea

Can females obtain good-genes benefits for their offspring by mating with older males? Age-based mate choice is controversial and relatively infrequently studied experimentally. In addition, it has recently become apparent that conflict over mating can generate substantial costs for both sexes. There is overt conflict over mating in the fly Sepsis cynipsea, and copulation dramatically reduces female longevity. We investigated whether male age influences the probability of mating, as well as its effect on several direct and indirect fitness measures, while further scrutinizing mating costs in S. cynipsea. Male age did not affect mating probability, female fertility, fecundity, offspring development time or survival. The fact that male age did not influence the likelihood of copulation is entirely consistent with the lack of detectable fitness benefits to females based on male age. However, the delay between copulation and egg laying was weakly positively associated with offspring survival as adults, as well as with clutch size. Interestingly, copula duration was negatively associated with the number of offspring that emerged as adults. The latter result resembles findings in Drosophila melanogaster, and may be indicative of additional costs of mating in this species