Chuck Bednar for redOrbit.com – @BednarChuck
Global warming is having an unusual effect on the bearded dragon lizards of Australia, causing the creatures to hatch as females and give birth to offspring even if they are genetically male, a new study published earlier this week in Nature has revealed.
According to the Associated Press, lead author Clare Holleley from the University of Canberra and her colleagues also found that hotter temperatures are altering the way in which the lizard’s gender is determined so much so that the female sex chromosome may disappear entirely.
“This is the first time we have proved that sex reversal happens in the wild in any reptile at all,” Holleley explained to the wire service on Wednesday. The research, he added, “is showing that climate extremes can very rapidly fundamentally alter the biology of an organism.”
How does that even happen?
Under normal conditions, the sex of a bearded dragon depends on a pair of chromosomes known as the Z chromosome and a W chromosome, National Geographic explained. When a lizard has two Z chromosomes, they develop as males, and when they have both a Z and a W, they become females. That changes, however, when temperatures start to increase.
When dragon eggs are incubated at 34 degrees Celsius or hotter, their bodies ignore the regular instructions from their sex chromosomes, meaning that if even half of them are genetically male (ZZ), every last one of them will hatch as females. While scientists know of other creatures that have their gender decided by incubation temperature, bearded lizards were not one of them.
Holleley’s team captured and examined the genetic sex markers of 131 bearded dragons caught in the wild, and found that 11 of them were outwardly female and could produce offspring, but had the ZZ chromosomes of a genetic male. Furthermore, this radical change in how the lizards determine their gender took place suddenly, over the course of just a single generation.
Holleley told Nat Geo that she doesn’t understand entirely how this change took place, because the genetics responsible for sex determination in lizards are poorly understood. The authors said they plan to look for the gene responsible and determine how it is regulated by temperature, and wrote that their study “adds to concern about adaptation to rapid global climate change.”
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