By examining research on global patterns of amphibian diversification over hundreds of millions of years, De Lisle and Rowe discovered that “sexually dimorphic” species – those in which males and females differ in size, for example – are at lower risk of extinction and better able to adapt to diverse environments.

Their work suggests the ability of males and females in sexually dimorphic amphibian species to independently evolve different traits – such as size – helps them survive extinction threats that kill off others, says De Lisle.

He says classic ecological theory would not have predicted that about amphibians, a class of vertebrates that includes frogs, toads, salamanders, newts and caecilians.

The conventional school of thought believes different-sized sexes of the same species take up more resources and are less able to adapt and diversify than species where ecologically relevant traits like size are basically the same between males and females.