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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