Meeting Abstract
The evolution of sexual dimorphism is predicted to occur through reductions in between-sex genetic correlations for shared traits, but the mechanisms that facilitate this process remain largely speculative. We hypothesize that the sex-biased regulation of autosomal genes by sex steroids is a mechanism of general importance in the reduction of between-sex genetic correlations. Using a paternal half-sibling breeding design in captive brown anole lizards (Anolis sagrei), we show that the development of sexual dimorphism in body size is mirrored by the ontogenetic breakdown of between-sex genetic correlations for body size and growth rate. Using transcriptome data, we show that sex-biased gene expression also increases dramatically between ontogenetic stages bracketing this breakdown of genetic correlation, particularly for autosomal genes involved in growth, metabolism, and cell proliferation. Mechanistically, we show that treatment of females with testosterone stimulates the expression of male-biased genes while inhibiting the expression of female-biased genes, thereby inducing male-like phenotypes at both organismal and transcriptomic levels. Collectively, these results support the hypothesis that hormones with sex-specific patterns of circulation, such as testosterone, can facilitate the developmental breakdown of between-sex genetic correlations by orchestrating sex-specific gene expression. To to test this hypothesis directly, we present data from an experiment in which we manipulated testosterone levels in the context of a half-sibling breeding design to determine whether and how this sex-specific hormone structures patterns of within- and between-sex genetic correlation.
