Kyle Hilliard

Date of Award

January 2019

Document Type


Degree Name

Master of Science (MS)



First Advisor

Turk Rhen


Sex-determining mechanisms in fish and reptiles are incredibly diverse. We first review sex-determination in these groups, including approaches that can be used to identify sex-determining genes and the large body of research showing genetic variation for sex ratio in species with temperature-dependent sex determination (TSD). We then show that sex ratio variation among clutches is due to additive genetic effects in one TSD species, the common snapping turtle. This finding contradicts previous claims that non-genetic maternal factors such as yolk steroid hormones are driving sex determination in this species. Heritable variation for sex determination in the snapping turtle may allow populations to evolve in response to global warming and avoid population decline due to highly skewed sex ratios.