Due to global warming, lizards change their sex

Climate change has had a powerful effect on Australian reptiles: in bearded agamas, the genetic system for determining sex has been disrupted due to abnormal heat, as a result of which more and more males are transformed into females. About this, scientists reported on the pages of the journal Nature.

It is known that the sex of many reptiles is determined not only by a set of chromosomes (for agamas this is Z and W: the set of ZZ for males and ZW is for 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 chromosomal system has been supplanted by temperature.

Arthur George and his colleagues at the University of Canberra have been working with bearded agamas in the states of Queensland and New South Wales since 2003. It turned out that from 2003 to 2011, due to abnormally hot weather, the proportion of females (which are 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 turned into moms become better moms,” George notes.

When transvestite females mated with ordinary males, their offspring only had Z chromosomes. Thus, global warming forces normal females out of a population and threatens to destroy the chromosomal sex determination system. The sex of the future agamas is increasingly chosen according to the temperature of the environment where the eggs are located.

Although this method helps lizards respond quickly to climate change, creating an optimal balance between males and females, its predominance will have the opposite effect: an unexpected rise in temperature risks leading to a sharp drop in the number of individuals of the sexes and thus threatens the population with extinction.