Costs of sperm production may lead to prudence in male sperm allocation and also to male mate choice. Here, we develop a life history-based mutual mate choice model that takes into account the lost-opportunity costs for males from time out in sperm recovery and lets mate competition be determined by the prevailing mate choice strategies. We assume that high mating rate may potentially lead to sperm depletion in males, and that as a result, female reproduction may be limited by the availability of sperm. Increasing variation in male quality leads, in general, to increased selective mate choice by females, and vice versa. Lower-quality males may, however, gain access to more fecund higher-quality females by lowering their courting rate, thus increasing their sperm reserves. When faced with strong male competition for mates, low-quality males become less choosy, which leads to assortative mating for quality and an increased mating rate across all males.
Metrics details. Conflicts of interest between the sexes are increasingly recognized as an engine driving the co- evolution of reproductive traits. The reproductive behaviour of Drosophila montana suggests the occurrence of sexual conflict over the duration of copulation. During the last stages of copulation, females vigorously attempt to dislodge the mounting male, while males struggle to maintain genital contact and often successfully extend copulations far beyond the females' preferred duration. By preventing female resistance, we show that females make a substantial contribution towards shortening copulations. We staged matings under different sex ratio conditions, and provide evidence that copulation duration is a form of male reproductive investment that responds to the perceived intensity of sperm competition as predicted by game theoretical models.
Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg  during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase males' chance of reproductive success. Sperm competition is often compared to having tickets in a raffle ; a male has a better chance of winning i.
Metrics details. Ever since Darwin, evolutionary biologists have studied sexual selection driving differences in appearance and behaviour between males and females. An unchallenged paradigm in such studies is that one sex usually the male signals its quality as a mate to the other sex usually the female , who is choosy in accepting a partner. Here, we hypothesize that in polygamous species these roles change dynamically with the mating status of males and females, depending on direct reproductive costs and benefits of multiple matings, and on sperm competition. We test this hypothesis by assessing fitness costs and benefits of multiple matings in both males and females in a polygamous moth species, as in moths not males but females are the signalers and males are the responders.