A shared genetic basis for sexually antagonistic male and female adaptations in the toothed water strider

Sexual conflict can drive the divergence of male and female phenotypes and several cross-species comparative analyses have documented patterns of correlated evolution of sex-specific traits that promote the evolutionary interests of the sexes. However, male-female coevolution can be highly dynamic. Moreover, if male and female traits do not have an entirely distinct genetic basis, this can have profound effects on their coevolutionary dynamics. Here, we use water striders, a well-studied model system for sexually antagonistic coevolution, and ask whether sex-specific phenotypic adaptations covary across populations and whether they share a common developmental genetic basis. Using comparative analyses both at the population and species levels, we document an association between a derived male mate-grasping trait and a likely female anti-grasping counteradaptation in the toothed water strider Gerris odontogaster. Interestingly, in one population where males did not express their derived grasping trait, females had also regained the ancestral morphology. We then used experimental manipulation of gene expression, and show that these male and female traits are both linked to a common developmental genetic program containing Hox and sex determination genes, despite the fact that they are different structures on different segments. Our work thus suggests that the pleiotropic nature of developmental genetic programs can blur the distinction between inter- and intralocus genetic conflict.