Conservation of social effects (Ψ between two species of despite reversal of sexual dimorphism.

Indirect genetic effects (IGEs) describe the effect of the genes of social partners on the phenotype of a focal individual. Here, we measure indirect genetic effects using the "coefficient of interaction" (Ψ) to test whether Ψ evolved between and . We compare Ψ for locomotion between ethanol and nonethanol environments in both species, but only utilizes ethanol ecologically. We find that while sexual dimorphism for locomotion has been reversed in , there has been no evolution of social effects between these two species. What did evolve was the interaction between genotype-specific Ψ and the environment, as  varies unpredictably between environments and  does not. In this system, this suggests evolutionary lability of sexual dimorphism but a conservation of social effects, which brings forth interesting questions about the role of the social environment in sexual selection.