Amphibians Show That Shrinking Won't Always Avoid Extinction

Size does indeed matter, even for avoiding extinction, but not in the way many scientists have long suspected. A new study of amphibians argues that growing smaller to take up less resources won't always help a species avoid extinction in the face of a shrinking habitat, climate change, and disease. Instead, it is argued that dimorphism - where males and females are different sizes - give a species a better shot.

Past studies have implied that in most situations where there is a potential for extinction, a species as a whole would do best to rapidly shrink in size. In this way, members of that species would eat less, allowing for more to survive off limited resources. A larger population, in turn, would give the threatened species more chances to develop helpful adaptations with each generation.

Nature World News previously reported that experts now suspect that dinosaurs who survived their way through several extinction events to evolve into modern birds likely pulled off this feat only after rapidly shrinking. Other work has shown that even today, climate change could be making salamanders and even goats smaller.

However, while this may hold true for many declining frogs and toads as well, it might not be the help researchers thought it was.

A study recently published in the journal Proceedings of the Royal Society B details how different sizes between sexes may help struggling amphibian species more than uniform shrinking.

By examining global data on amphibian diversification over hundreds of millions of years (as detailed in past studies), researcher Stephen De Lisle and Locke Rowe at the University of Toronto found that sexual dimorphic species have fared far better in the face of numerous extinction events.

Today, between 30 and 40 percent of the world's approximately 7,000 species of amphibians are currently in danger of extinction - more than any other animals on Earth. That's despite some species, like the aforementioned salamanders, are going through the arguably "good" change of being smaller and taking up fewer limited resources.

"I think if our results bear on mass extinction at all, it suggests we maybe should start looking more closely at the traits of some of the species that are going extinct," De Lisle said in a statement.

He added that their work indicates that if two genders adapt differently thanks to different sizes, it increases a species' chance of developing helpful adaptations overall.

"Scientists might start thinking in a new way about how other traits, like sex differences in habitat use or diet, might play a role."

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