AsianScientist (Jun. 20, 2016) – When the males of the large, spectacular Australian desert bearded dragon lizard undergo sex reversal, the sex-reversed ‘females’ display more male characteristics than even the male-bodied lizards, according to research from the University of Sydney published in Proceedings of the Royal Society.
In most species of animals, an individual’s sex is determined either by their genes (sex chromosomes) or by the conditions they encounter as they are developing. For example, whether a crocodile embryo becomes a male or a female depends on how warm it is within the nest.
But in a bearded dragon, things get much more complicated. Although sex is usually determined by sex chromosomes, an unusually warm nest can override that effect. As a result, hot nests produce lizards that are genetically male but develop into females. Those sex-reversed ‘females’ have unusual personalities as well as unusual genetics.
First author Li Hong and collaborators filmed normal male and female dragons and their sex-reversed brothers (now sisters) in standard trials to measure boldness, activity level and exploratory behavior. The sex-reversed animals were bolder and more active than ‘normal’ females and even bolder than most ‘normal’ males.
So, sex reversal changes a male dragon into a female in terms of reproductive biology—but he/she retains many male-like personality characteristics.
Co-author Professor Rick Shine, from the University of Sydney’s School of Life and Environmental Sciences, remarked that this could make them more successful in the wild—accelerating the rate that a population can shift from one form of sex determination (chromosomal) to a different system (temperature-driven).
Biologists have generally expected such an evolutionary transition to happen slowly—over thousands of years—but a behavioral difference between genetically-determined and temperature-determined females could give one type of female a major advantage over the other, speeding up the replacement process dramatically.
“One of the most interesting aspects is that, under natural conditions, we can see a process producing individuals with the bodies of females but, at least to some degree, with the brains of males,” Shine said. “Sex in dragons is clearly a much more complicated matter than we have assumed,” Shine said.
The article can be found at: Li et al. (2016) The Behavioural Consequences of Sex Reversal in Dragons.
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Source: University of Sydney; Photo: Arthur Georges.
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