Male body size affects female lifetime reproductive success in a seed beetle

摘要

Males of many animal taxa allocate resources largely to mate acquisition and defence, contributing little more than gametes to embryo production. In many insects, however, males transfer large spermatophores or ejaculates to females during mating, and extragametic substances derived from these packages are used for somatic maintenance and egg production by the recipient females (e.g. Boggs 1981). Females receiving multiple male contributions lay more (Ridley 1988) and often larger eggs (Fox 1993a) than do once-mated females, indicating large effects of male-derived nutrients on female reproduction. Furthermore, large males produce larger ejaculates or spermatophores than small males (Fox et al. 1995), and females of some insects preferentially mate with large males (Thornhill & Alcock 1983). To date, however, there has been no clear demonstration in any insect of a direct fitness advantage to mating with large males (e.g. Pitnick 1991; but see Gwynne 1988). Here, we provide evidence that variation among males in body size has a direct effect on female reproductive success (lifetime fecundity and egg size) in a seed beetle, Stator limbatus, and suggest that this is likely to be caused by extragametic nutrients being transferred in male ejaculates during mating.