Geographic variation in pivotal temperatures for sex determinations in reptiles.

Offspring sex is determined by incubation temperature in many reptiles. These animals are faced with the challenge of producing viable sex ratios when their geographic distribution spans a wide thermal range. Attributes of the mother or embryo must be adjusted, in evolutionary terms, in order to maintain sex ratios near unity. One such attribute is pivotal temperature, the temperature that separates male-producing temperatures from female-producing temperatures. We will investigate geographic variation in pivotal temperatures among populations of the water dragon, a species with temperature-dependent sex determination, to gain insight into how reptiles with TSD evolve to persist across wide climatic ranges, and how their survival may be compromised by climate change.