Nest-site selection in two eublepharid gecko species with temperature-dependent sex determination and one with genotypic sex determination

At present, most turtles, all crocodilians, and several lizards are known to have temperature-dependent sex determination (TSD). Due to the dependence of sex determination on incubation temperature, the long-term survival of TSD species may be jeopardized by global climate changes. The current study was designed to assess the degree to which this concern is justified by examining nest-site selection in two species of Pattern II TSD geckos (Eublepharis macularius and Hemitheconyx caudicinctus) and comparing these preferences with those of a species with genotypic sex determination (GSD) (Coleonyx mitratus). Temperature preferences for nest sites were found to be both species-specific and female-specific. While H. caudicinctus females selected a mean nest-site temperature (32.4 degrees) very close to the upper pivotal temperature (32 degrees C) for the species, E. macularius females selected a mean nest-site temperature (28.7 degrees C) well below this species' lower pivotal temperature (30.5 degrees C). Thus, the resultant sex ratios are expected to differ between these two TSD species. Additionally, nest-site temperatures for the GSD species were significantly more variable (SE = +/-0.37) than were temperatures for either of the TSD species (E. macularius SE = +/- 0.10; H. caudicinctus SE = +/-0.17), thereby further demonstrating temperature preferences within the TSD species. (C) 2000 The Linnean Society of London.