The repeatability of a sexual conflict over mating

Abstract

Measuring individual variation in mating behaviour is an integral part of studies of sexual selection and of considerable theoretical importance. Few studies, however, have examined individual variation in mating behaviour in a sexual conflict system and considered how individual variation influences the strength and consistency of the resulting sexual selection. We examined variation in mating behaviour of male and female pairs in the seaweed fly, Coelopa frigida. Sexual selection in seaweed flies occurs as a result of a sexual conflict over mating, with larger males generally able to overcome female rejection responses. We explored male and female mating conflicts and examined the variation in conflict outcomes within and between pairs. First, female willingness to mate was unaffected by short-term mating experience, allowing us to examine repeated interactions between a male and a female. Second, the outcomes of the sexual conflict over mating (copulation or rejection), and components of the mating interaction (number of copulations and time the male is mounted), were strongly repeatable. Third, the patterns of sexual selection on male size were consistent across mounts. Individual pairs consistently gave the same outcome to the mating conflict and yielded consistent sexual selection. Sexual conflict systems can thus be studied in the same way as those with more traditional forms of sexual selection and yield important insights into the links between variation in mating behaviour and sexual success.