Meeting Abstract
Sex-ratio theory predicts that, all else being equal, mothers that produce offspring of the rarer sex engender a fitness benefit. Implementing such a strategy might be less challenging in species with environmental sex determination relative to those with genotypic sex determination. Reptiles with temperature-dependent sex determination (TSD) could conceivably choose nest sites with the thermal characteristics (e.g., shade cover) to readily overproduce the rarer sex. To test this hypothesis, we seeded three secure outdoor ponds for a two-year period with different sex ratios (3:1, 1:1, and 1:3) of adult painted turtles (Chrysemys picta), a reptile species with TSD. We then quantified traits related to nesting behavior that could influence offspring sex ratio, including nesting date, nest depth, and nest shade cover. Preliminary analyses revealed no relationship between the adult sex ratio treatments and any measured nest traits, thus rejecting our hypothesis. If adaptive sex allocation occurs in this system, it instead may manifest via maternal epigenetic predisposition of offspring sex or in response to a phenomenon other than adult sex ratio.
