Sunday, July 5, 2015

Sex reversal triggers rapid transition from genetic to temperature-dependent sex.


Hatchling Bearded Dragon
A climate-induced change of male dragons into females occurring in the wild has been confirmed for the first time, according to University of Canberra research recently published on the cover of international journal Nature.

The researchers, who have long studied Australia's bearded dragon lizards, have been able to show that a reptile's sex determination process can switch rapidly from one determined by chromosomes to one determined by temperature.

Lead author Dr. Clare Holleley, a postdoctoral research fellow at the University of Canberra's Institute for Applied Ecology, explained: "We had previously been able to demonstrate in the lab that when exposed to extreme temperatures, genetically male dragons turned into females."

"Now we have shown that these sex reversed individuals are fertile and that this is a natural occurring phenomenon."

Using field data from 131 adult lizards and controlled breeding experiments, Dr Holleley and colleagues conducted molecular analyses which showed that some warmer lizards had male chromosomes but were actually female.

"By breeding the sex reversed females with normal males, we could establish new breeding lines in which temperature alone determined sex. In doing so, we discovered that these lizards could trigger a rapid transition from a genetically-dependent system to a temperature-dependent system," she said.

"We also found that sex-reversed mothers -- females who are genetic males -- laid more eggs than normal mothers," Dr Holleley said. "So in a way, one could actually argue that dad lizards make better mums."

University of Canberra Distinguished Professor Arthur Georges, senior author of the paper, also highlighted the importance that these discoveries have in the broader context of sex determination evolution.

"The mechanisms that determine sex have a profound impact on the evolution and persistence of all sexually reproducing species," Professor Georges said.

"The more we learn about them, the better-equipped we'll be to predict evolutionary responses to climate change and the impact this can have on biodiversity globally."



Holleley CE, O'Meally D, Sarre SD, Marshall Graves JA, Ezaz T, Matsubara K, Azad B, Zhang X, Georges A.
Sex reversal triggers the rapid transition from genetic to temperature-dependent sex. Nature, 2015; 523 (7558): 79 DOI: 10.1038/nature14574

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