Meeting Abstract
Fisherian sex-ratio theory predicts sexual species should have a balanced primary sex ratio. However, organisms with environmental sex determination (ESD) are particularly vulnerable to sex ratio skews as environmental conditions are variable. Theoretical work has modeled sex-ratio dynamics for animals with ESD with regard to two traits predicted to be responsive to sex-ratio selection: (1) maternal nest-site choice and (2) sensitivity of embryonic sex determination to environmental conditions, and much research has since focused on how these traits influence offspring sex ratios. However, relatively few studies have estimated univariate quantitative genetic parameters for these two traits, and the existence of phenotypic or genetic covariances among these traits has not been assessed. Here, we leverage studies on three species of reptiles (two turtle species and a lizard) with temperature-dependent sex determination (TSD) to assess the phenotypic covariance between maternal nest-site choice and the thermal sensitivity of the sex-determining pathway. These studies measured maternal nesting behaviors that relate to nest temperature, and assessed the sex ratio of offspring incubated under controlled conditions. A strong covariance between these traits would maximize the efficiency of sex-ratio selection. However our results indicated no such covariance between nest-site choice and thermal sensitivity in the three study species. These results suggest that nest-site choice and thermal sensitivity of sex determination are able to evolve independently. Such information is critical to understand how animals with TSD will respond to rapidly changing climate.
