TSD in Other Reptiles

Among the other reptiles that TSD has been found in, crocodilians are the only group that employs strictly TSD as a mechanism for sex-determination (Bull, 1980). TSD has also been found in a large number of turtle species and a few lizards as well; it has not however, been documented in snakes (Pieau et al, 1995). All three reptilians groups in which TSD is present have been documented to use Pattern II of TSD, in which low and high incubation temperatures yield females and intermediate temperatures yield offspring sex ratios that a biased toward males, leading some researchers to speculate that it is the most primitive form of TSD (Pieau et al, 1995).

The lizard Agama agama, one of the first reptiles in which TSD was documented. Photo by Jon Loman, used with permission.

Alligator mississippiensis. Photo by Michael Dorcas, used with permission.

Juvenile Alligator mississippiensis. Photo by J.D. Willson, used with permission by Michael Dorcas.

Figure 4

Figure 4 depicts the phylogenetic tree for lizards. Those species that exhibit ESD are underlined. Figure 4 adapted from: Janzen, F. J. and G. L. Paukstis. “A Preliminary Test of the Adaptive Significance of Environmental Sex Determination in Reptiles.” Evolution 45 (1991): 435-440. JSTOR. Davidson Coll. Lib., Davidson, NC. 15 Sept. 2004.


Questions? Email me kykinsell@davidson.edu