Meeting Abstract
Many endocrine networks are composed of autosomal genes that are shared between the sexes, which could theoretically impede the evolution of sexual dimorphism. However, hormones with sex-specific circulation (e.g., testosterone, or T) can be coupled and decoupled from the expression of shared regulatory networks to produce diversity in patterns of sexual dimorphism. We compared lizard species with male-biased sexual size dimorphism (SSD, two species) and female-biased SSD (one species) to test for the evolution of differences in how a sex-biased hormone (T) regulates sex-specific gene expression. Across the whole transcriptome, we found that while T stimulates the expression of male-biased genes, it inhibits the expression of female-biased genes for all three species. However, we found that those genes with male-biased expression in male-larger species tend to exhibit female-biased expression in the female-larger species. Similarly, we found that genes that tend to be stimulated by T in male-larger species tend to be inhibited by T in female-larger species. Finally, we found that these effects were observed specifically in growth regulatory gene networks, where T stimulated expression of growth-promoting genes such as IGF-1 in male-larger species, whereas these same genes were inhibited by T in female-larger species. Our research reveals how the relationship between a single pleiotropic hormone (T) and both the whole transcriptome and shared regulatory networks could facilitate the evolution of sexual dimorphism.
