Effects of incubation temperature on sex determination in a community of neotropical freeshwater turtles in southern Mexico

Abstract

Incubation temperature has been shown to control sex determination (TSD) in both suborders of living turtles, including freeshwater, terrestrial, and sea turtles. This study combines field and laboratory data freom four neotropical endemic species (Dermatemys mawii, Staurotypus triporcatus, Claudius angustatus, and Kinosternon leucostomum) and two of temperate zone origin (Chelydra serpentina and Trachemys scripta). The sex of hatchlings incubated in natural nests and controlled laboratory temperatures was studied. Adult sex ratios in natural populations were determined by mark and recapture studies. Staurotypus and Claudius appear to have genetic sex determination (GSD) while TSD occurred in the other four species. Threshold temperatures of both Trachemys and Chelydra were lower in these Neotropical populations than in those studied in Temperate Zone climates. Natural populations of species with TSD were found to have variable adult sex ratios, skewed towards one sex or the other. These variations in sex ratio could sometimes be explained by nest site ecology.