Meeting Abstract

25.6  Friday, Jan. 4  Sex-ratio selection influences nesting behavior in a reptile with environmental sex determination MITCHELL, T.S.*; MACIEL, J.; JANZEN, F.J.; Iowa State University; Iowa State University; Iowa State University timmitch@iastate.edu

Evolutionary theory predicts that dioecious species should produce an even primary sex ratio, which will be maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to experiencing sex-ratio skews, because environmental conditions vary through space and time. For reptiles with temperature-dependent sex determination (TSD), nest-site choice is a behavioral maternal effect that may respond to sex-ratio selection, as mothers can adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet researchers have not provided convincing evidence that sex-ratio selection influences nesting behaviors. Here we provide experimental evidence that sex-ratio selection is an important component of nest-site choice in a reptile with TSD. We compare painted turtle (Chrysemys picta) neonates from eggs incubated and hibernated in maternally selected nest sites to those in randomly-selected nest sites and observe no difference in hatching success or overwinter survival, but detect a profound difference in offspring sex ratios. As predicted by theory, our results suggest that sex-ratio selection has shaped maternal nesting behavior in ways likely to enhance maternal fitness by producing a balanced primary sex ratio.