By Joshua Sokol. Zoologger is our weekly column highlighting extraordinary animals — and occasionally other organisms — from around the world. Male lizards from Australia become super-fecund females in hot weather. Rising temperatures could lead to a sex change avalanche that pushes populations — and perhaps the entire species — towards a society without adult males.
Lizard Swaps Mode of Deciding Its Sex | The Scientist Magazine®
Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies 42 species of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes.
Zoologger: The lizard that changes its sex to suit the weather
Others are influenced by environmental conditions, such as temperature. Certain lineages appear to have flipped from genetic- to thermal-based sex determination over the course of evolutionary time, but no experimental data have shown exactly how these transitions occurred. Now, researchers have caught a real-time glimpse of a sex-determination switch in bearded dragons Pogona vitticeps native to Australia. About one-fifth of wild-caught female lizards carried the male sex chromosomes ZZ , according to a study published in Nature today July 1 , and these animals were able to mate and produce offspring whose sex was determined by the temperature at which the eggs were incubated. The findings suggest that sex reversal—the development of females with male chromosomes—may be a mechanism for the transition from a genotypic to a thermal-based mode of sex determination in a population.
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