Until now animals were assumed to use one mechanism or the other, with reptiles such as crocodiles, turtles, and tortoises relying on temperature, and mammals, birds, and most amphibians depending on genes.
"Theory in Tatters'
A dual system for determining sex has also been suggested for another Australian lizard, the three-lined skink, by a team led by Rick Shine, professor of evolutionary biology at the University of Sydney.
Shine said that the new findings "verify a remarkable phenomenon."
"The evidence that nest temperatures can override sex chromosomes is absolutely clear-cut," he commented.
"The work is exciting because it suggests that a long-held dogma in this research field—that in any given population, sex is determined by a single process—is now in tatters.
"The factors that determine an animal's sex are truly basic to its biology, and it's becoming increasingly clear that we don't really understand what those factors are, at least in some major groups of animals.
"I suspect that future studies will show that many kinds of animals have far more complex sex-determining systems than we currently imagine," he added.
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