A shift in egg-incubation temperature can result in a genetically male lizard having a mix of male and female traits.
The sex of some reptile species is determined by genetics, but in others it depends on egg-incubation temperature. Richard Shine at the University of Sydney in Australia and his colleagues studied hatchlings and juveniles of the central bearded dragon (Pogona vitticeps; male pictured). In this species, sex is normally controlled genetically, but incubation temperatures of 32 °C and above can produce sex-reversed females from male embryos. The team incubated eggs at constant temperatures between 26 °C and 34 °C, and found that although sex-reversed females are capable of laying eggs — and even produce more eggs than genetic females — they are similar to males in their morphology and behaviour.
This mix of traits could enhance fitness under certain conditions, which could cause a rapid elimination of sex-determination genes, the authors say.