JANES, D.E.; WAYNE, M.L.; Harvard Univ.; Univ. of Florida: Quantitative Genetic Variation in Sex-Determining Response to Incubation Temperature in Leopard Geckos

Among vertebrates, sex is determined by one of two recognized mechanisms: environmental or genetic sex determination in which sex is determined by incubation environment or genetic contribution of parents, respectively. The adaptiveness of one mechanism over the other is unclear and our understanding of the evolution of environmental sex determination (ESD) is obscured by the lack of evidence for genetic architecture. In this study, an environmentally sex-determined reptile, Leopard Geckos, Eublepharis macularius, were mated to test for a genotype x environment interaction (GEI) in their sex-determining response to incubation temperature. Five sires were each mated to five dams. The offspring of each sire(dam) were divided into egg groups exposed to one of three incubation temperatures. The sex of all hatchlings was tested against temperature, dam(sire), temperature x dam(sire), and their immediate incubation environment, the egg group. We report a significant GEI (temperature x dam(sire)) in the offspring sexes of our experimental groups of E. macularius. Pairs of sires and dams produced different sex ratios at the same and different incubation temperatures. Evidence of genetic variation for ESD has been elusive. Our conclusion of GEI suggests a genetic underpinning to ESD that could be acted upon by natural or artificial selection.