Variation in the cost to females of the sexual conflict over mating in the seed bug, Lygaeus equestris

Conflict between males and females over reproduction influences the evolution of numerous aspects of reproductive behaviour, including how frequently individuals mate. Typically, females optimize the benefits of mating with a limited number of copulations, whereas males may benefit from increasing the number of copulations, leading to a sexual conflict over female mating rate. While this conflict is theoretically straightforward, empirically much less is known about how commonly it is realized. We quantified the costs of mating for females from two populations of the promiscuous Lygaeus equestris seed bug. By varying the number of males kept with a female, we found that increased matings led to decreased longevity and fecundity, and that the detrimental effects of mating varied between the two populations. When females mated only once, male weight positively influenced egg production, as did copulation duration for lighter females, suggesting that females may benefit from mating with certain males, albeit a limited number of times. Our results show that degree of promiscuity may not be a good predictor of mating costs (i.e. how costly the sexual conflict over mating actually is) and that life history differences between populations have the potential to influence the extent to which the sexes come into conflict.