The significance of disentangling shared mating traits: A review of empirical approaches

Abstract Sexual conflict has been shown to be widespread between males and females. In most cases, shared mating traits like copulation duration or sperm transfer speed are at the heart of such conflicts as the sexes usually have different optima. The contribution of both sexes to such unavoidably shared mating traits is highly understudied as most research focuses on one sex at a time. Moreover, a critical evaluation of the methodology to systematically disentangle male and female effects is lacking. Here we discuss different methods that are suitable for estimating the sex-effects on these shared copulatory and post-copulatory traits. Approaches embracing inter-individual differences, between-population comparisons and experimental manipulations can potentially overcome the methodological challenges of disentangling shared mating traits, promising novel insights into the intricacies of sexual selection and conflict. We clarify the strengths and pitfalls of these different methods and suggest statistical estimates based on variance decomposition that should generally be calculated in such studies. Together with tailored experiments, these estimates can allow us to understand the extent to which the sexes are in control, ultimately providing information about the direction and strength of selective pressures acting on sexual traits.