ABSTRACT
Temperature-dependent sex determination (TSD) occurs when males or females are differentially produced according to the incubation temperature (Bull, 1983). Since the discovery of TSD in a squamate by Charnier (1966), this pattern of sex determination has been described in various reptiles: all crocodilians (Deeming, 2004), tuataras (Nelson et al., 2004), some squamates (Harlow, 2004), and 64 out of the 79 studied turtle species (Ewert et al., 2004). Other reptile species exhibit genotypic sex determination (GSD), where sexual phenotype is independent of embryonic incubation temperature. GSD in reptiles is sometimes linked with heteromorphic sex chromosomes, with males or females being the heterogametic sex. However, many species with GSD do not exhibit strong differentiation of sex chromosomes. Overall, the presence of dimorphic sex chromosomes is not necessarily mutually exclusive of TSD, as has been demonstrated in various amphibians (Chardard et al., 2004) and one lizard (Shine et al., 2002).
