Climate Change: Lizards Switch Sex

Central bearded dragons, a type of lizard in Australia's Western Queensland, get ahead in tough and warming times by producing more females. Thus, they have more eggs with the intention of colonizing areas faster, researchers theorize. The lizards are doing this in a somewhat unusual way: They're switching genders in a move that has been linked with increasing temperatures, researchers from the University of Canberra say in a release.

The lizards, Pogona vitticeps, can be born with male chromosomes, then become females capable of producing twice as many eggs as standard females, as the researchers reported recently in the journal Nature. https://www.nature.com/nature/journal/v523/n7558/full/nature14574.html

This is the first case of sex-reversal seen in a terrestrial vertebrate in the wild, said Professor Arthur Georges, senior author of the paper, in the release.

The researchers first studied the lizards in labs, then analyzed field data from 131 adult lizards and controlled breeding experiments, concluding through molecular analyses that some warmer lizards had male chromosomes but were actually female. All in all, 11 of the lizards were in the latter category.

At lower temperatures, a female determines the sex of her offspring by passing on either a Z or W chromosome (according to the system used for birds, some fish, and some reptiles). If eggs are exposed to temperatures above 90 degrees Fahrenheit, males can reverse their sex and become females, even without the differentiating W chromosome, said the release.

"Now we have shown that these sex-reversed individuals are fertile and that this is a natural occurring phenomenon," says Dr. Clare Holley, a postdoctoral fellow at the University of Canberra's Institute for Applied Ecology, according to the university release.

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