Sex Determination in Gekkota

The Leopard Gecko, Eublepharis maculatus, is
one of the best studied geckos in terms of its
sex-determination mechanism. JCM
The known number of sex determining mechanisms and variations on them seem to be ever increasing in reptiles as we learn more about them. There are species with male and female heterogamety - sex chromosomes; species with temperature-dependent sex determination, and species with both systems. Within each of these there seems to be many variations. Geckos (Gekkota) are the second most specious lineage of lizards (skinks are the first) with more than 1300 species placed in six different families. The diversity of geckos and their sex determination mechanisms make them excellent candidates for studying the evolution of these mechanisms and current knowledge suggests that geckos have transitioned from one mechanism to another many times during their evolutionary history. Yet, of the 1300 species, relatively few (about 46) have been examined for the mechanisms they use. Tony Gamble of the University of Minnesota has recently summarized the sex determination mechanisms used by geckos in various lineages and discovered that at least 8 or 9 transitions have occurred within the last 150 million years, despite the low number of species that have been examined to date. The Carphodactylidae has not been studies at in this regard, and the Diplodactylidae, Phyllodactylidae, and Sphaerodactylidae are poorly known in terms of how they determination the sex of their offspring. Gamble’s work suggests the ancestral gecko used male heterogamety as the determining mechanism with temperature-dependent sex determination evolving 5 times independently from a genetic sex determination ancestor.



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