Data from: Ecological character displacement between the sexes

Theory suggests the evolution of sexual dimorphism in ecologically
relevant traits can evolve purely through competition between the sexes
for a shared resource. Although more parsimonious hypotheses exist for the
evolution of ecological sexual dimorphisms, there are some
underappreciated reasons to expect that competition may often play some
role in the evolution of sexual dimorphism. Here, we build on past work to
outline a set of sufficient criteria to demonstrate a role for resource
competition in the evolution of sexual dimorphism, the most critical of
which is that resource competition can be directly linked to sexual
divergence along the axis of ecologically-relevant dimorphism. We then
compare the geometry of fitness surfaces across experimental manipulations
of density and sex ratio in a semiaquatic salamander (Notophthalmus
viridescens). We find consistent disruptive selection on multivariate
sexual dimorphism in feeding morphology, which increases in strength with
density. Fitness and the strength of divergent selection are
negative-frequency dependent in the manner expected under
competition-driven divergence between the sexes. Our results constitute
direct evidence of resource competition as a driver of sexually-antagonist
selection and consequently the evolution of sexual dimorphism, showing how
cause and effect can be separated in studies of ecological sexual
dimorphism. We suggest resource competition may contribute to sexual
divergence jointly with other sources of sex-biased selection, especially
when ecological opportunity is sex-specific. EndDryadContent