Genotype x environment interaction is weaker in genitalia than in mating signals and body traits in Enchenopa treehoppers (Hemiptera: Membracidae)

Theory predicts that selection acting across environments should erode genetic variation in reaction norms; i.e., selection should weaken genotype x environment interaction (G x E). In spite of this expectation, G x E is often detected in fitness-related traits. It thus appears that G x E is at least sometimes sustained under selection, a possibility that highlights the need for theory that can account for variation in the presence and strength of G x E. We tested the hypothesis that trait differences in developmental architecture contribute to variation in the expression of G x E. Specifically, we assessed the influence of canalization (robustness to genetic or environmental perturbations) and condition-dependence (association between trait expression and prior resource acquisition or vital cellular processes). We compared G x E across three trait types expected to differ in canalization and condition-dependence: mating signals, body size-related traits, and genitalia. Because genitalia are expected to show the least condition-dependence and the most canalization, they should express weaker G x E than the other trait types. Our study species was a member of the Enchenopa binotata species complex of treehoppers. We found significant G x E in most traits; G x E was strongest in signals and body traits, and weakest in genitalia. These results support the hypothesis that trait differences in developmental architecture (canalization and condition-dependence) contribute to variation in the expression of G x E. We discuss implications for the dynamics of sexual selection on different trait types.