Climate change has had a powerful effect on Australian reptiles: in bearded agamas (Pogona vitticeps), due to the abnormal heat, the genetic system for determining sex is disrupted, as a result of which more and more males turn into females. Scientists reported this in the pages of the journal Nature.
It is known that the sex in many reptiles is determined not only by the set of chromosomes (in agamas, these are Z and W: the set of ZZ in males and ZW in females), but also by the temperature of the environment in which the eggs laid by them mature. However, for the first time in the wild, the chromosome system was supplanted by the temperature system.
Arthur Georges and his colleagues at the University of Canberra have worked with bearded agamas in Queensland and New South Wales since 2003. It turned out that from 2003 to 2011, due to abnormally hot weather, the proportion of females (complete in terms of anatomy, physiology and behavior, but with a “male” set of chromosomes, ZZ) increased from 6 to 22 percent.
Moreover, such "transvestites" turned out to be larger, healthier and able to lay about twice as many eggs as ordinary females. “Dads who turn into moms become better moms,” notes George.
When female “transvestites” mated with normal males, their offspring only had Z chromosomes. Thus, global warming is displacing normal females from the population and threatening to destroy the chromosomal sex determination system. The sex of future agamas is increasingly chosen in accordance with the temperature of the environment where the eggs are located.
Although this method helps lizards to quickly respond to climatic changes, creating an optimal balance between males and females, its predominance will lead to the opposite effect: an unexpected jump in temperature risks leading to a sharp drop in the number of individuals of one of the sexes and thus threatens the population with extinction.