Meeting Abstract

17-1   10:00 - 10:15  The Ancestral Modulation Hypothesis: using evolutionary history to predict mechanisms underlying sex-biased trait expression Anderson, AP*; Renn, SCP; Reed College; Reed College andersond@reed.edu http://andersonevolve.com

Sex-biased traits are a fascinating feature of evolution that manifest in nearly innumerable forms beyond those conventional patterns most often cited in explanations of sexual selection and natural selection. Sex-biased phenotypes ultimately feed back into sexual selection as well as drive species diversity and even speciation, thereby necessitating the need for a framework for studying sex-biased trait evolution. The molecular and physiological mechanisms involved in the production of sex-biased traits are seemingly disparate across species, yet identifying which mechanisms will evolve under different situations is critical for the understanding of the evolution of sex-biased traits. We advance the Ancestral Modulation Hypothesis (AMH) to predict the pattern of underlying mechanisms based on the specific evolutionary history of a sex-biased trait. The Type I Pattern, predicted whan a sex-biased trait emerges de novo, relies on the evolution of genomic elements to access existing sex-biased pathway for that sex. The Type II Pattern, predicted when a sex-biased trait undergoes evolutionary transitions from one sex to the other, relies on the evolution of hormone titers, or sensitivity to access the sex-biased pathway conventionally associated with the opposite sex. By using instances in which sex-biased traits manifesting in opposite sexes in closely related species and focusing on hormonal control mechanisms, we define an overarching hypothesis that will have bi-directional predictive power for molecular mechanisms, physiological manifestations and evolutionary processes.