Mate competition provides the opportunity for sexual selection which often acts strongly on males, but also the opportunity for sexual conflict that can alter natural selection on females. Recent attention has focused on the potential of sexual conflict to weaken selection on females if male sexual attention, and hence harm, is disproportionately directed towards high- over low-quality females, thereby reducing the fitness difference between these females. However, sexual conflict could instead strengthen selection on females if low-quality females are more sensitive to male harm than high-quality females, thereby magnifying fitness differences between them. We quantify the effects of male exposure on low- versus high-quality females in in each of two environments ('simple' and 'complex') that are known to alter behavioural interactions. We show that the effects of male harm are greater for low- compared to high-quality females in the complex but not the simple environment, consistent with mate competition strengthening selection on females in the former but not in the latter environment.

Much of sexual dimorphism is likely due to sex-biased gene expression, which results from differential regulation of a genome that is largely shared between males and females. Here we use allele-specific expression to explore cis-regulatory variation in Drosophila melanogaster in relation to sex. We test for sex differences in cis-regulatory effects as well as examine patterns of cis-regulatory with respect to two other levels of variation in sexual dimorphism: (i) across genes varying in their degree of sex-biased expression, and (ii) among tissues that vary in their degree of dimorphism (e.g., relatively low dimorphism in heads vs high dimorphism in gonads). We uncover evidence of widespread cis-regulatory variation in all tissues examined, with female-biased genes being especially enriched for said variation. A sizeable proportion of cis-regulatory variation is observed to have sex-specific effects, with sex-dependent cis effects being more frequent in gonads than in heads. Finally, we detect some genes with reversed allelic imbalance between the sexes. Such variants could provide a mechanism for sex-specific dominance reversals, a phenomenon important for sexually antagonistic balancing selection.