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The Leopard Gecko, Eublepharis maculatus, is one of the best studied geckos in terms of its sex-determination mechanism. JCM
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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.
Citation
Labels: evolution, geckos, sex-determination