Meeting Abstract
A central goal of evolutionary endocrinology is to understand how the pleiotropic effects of hormones facilitate or constrain the evolution of sexual dimorphism. Endocrine networks are conserved and shared between the sexes, which should impede the evolution of sexual dimorphism. However, hormones with sex-specific expression (e.g., testosterone, or T) could be coupled and decoupled from the expression of shared regulatory networks to produce diversity in patterns of sexual dimorphism. Our research addresses how a sex-biased hormone (T) pleiotropically regulates the expression of shared regulatory networks and sexual size dimorphism (SSD). First, we studied brown anoles, which have extreme male-biased SSD that develops as growth diverges between the sexes during development. We found that phenotypic divergence between the sexes was mediated by T and accompanied by an increase in sex-biased gene expression in the liver, an integrator of growth and energetics. Notably, expression of growth-regulatory insulin signaling/mTOR networks diverged between the sexes during ontogeny and was altered by exogenous T in both sexes. Second, we extended this work to test of how T impacts gene expression in lizards with both male- and female-biased SSD (spiny lizards). We found that T has the opposite impact on gene expression in growth-regulatory networks for species with female-biased SSD (eastern fence lizard), compared to male-biased brown anoles. This research reveals how the relationships between conserved regulatory networks and a single pleiotropic hormone (T) can facilitate the evolution of different patterns of sexual dimorphism.
