GONZALEZ, J/E; JANZEN, F/J; Iowa State University, Ames; Iowa State University, Ames: Inheritance of Nest-Site Choice in the Field in a Turtle with Temperature-Dependent Sex Determination
The sex of most turtles, including that of painted turtles (Chrysemys picta), is determined by incubation temperature. Because of this unusual mechanism of sex determination, the choice of nest site is important for determining the sex of the offspring, which ultimately influences the sex ratio of the population. Recent field studies have shown that female painted turtles choose nest sites based on the thermal microclimate at a particular location and that individual females choose thermally similar sites during each nesting event. The repeatability of this behavior suggests that there may be a quantitative genetic basis underlying nest-site choice. A preliminary test of this hypothesis was conducted by combining assays of molecular and phenotypic variation for 95 females from the focal population. We quantified overstory vegetation cover of nest sites and two highly variable microsatellite DNA markers for each female. Although more microsatellite loci and females remain to be examined, preliminary results indicate that the actual variance of relatedness (Var(r)) is positive but the heritability of nest-site choice is low (h2 = .000171). These initial results suggest that, although related females return to nest in the same geographic area, the turtles do not inherit microclimate nesting preferences from their mothers via substantive quantitative genetic factors. Thermally-based nest-site choice is therefore unlikely to serve as an evolutionary mechanism to ensure balanced sex ratios in this system
