It was earlier assumed that Natural Selection drove frogs to take the evolutionary step to reproduce on land as a way for parents to avoid aquatic predators who feed on the eggs and tadpoles.
The new study, published in the journal American Naturalist, showed that some frogs hide eggs on land to reduce competition from other males who also want to fertilise those eggs.
“We thought maybe it’s not just natural selection driving the adaptation to reproduce on land, maybe this is actually sexual selection,” said corresponding author Kelly Zamudio, Professor at Cornell University in Ithaca, New York.
In the study, researchers analyzed data on reproductive modes for two families of frogs – Hylidae, or tree frogs, and Leptodactylidae, including about 900 species that are mostly found in Central and South America.
Frogs are known to have up to 40 reproductive modes, with new ones still being discovered.
Some species build hidden chambers on land or females lay eggs in folded leaves or in bromeliads, others lay eggs in water and move them or their tadpoles to land, and others get rid of the tadpole stage entirely.
The study sheds light on evolutionary forces that drive diversity. Also, the results give conservationists insights on habitats and species that may need more protection, Zamudio said.
“More specialized reproduction modes, like the ones that are terrestrial, are less frequent, and typically, when species get threatened, because of climate change or habitat disturbance, the species that go first are the ones that are more specialised. They have requirements above and beyond just having a pond,” Zamudio noted.