Frogs leaped to take advantage of the global catastrophe that killed off the dinosaurs, scientists have discovered.
New research shows that 88% of frog species alive today owe their existence to the meteor impact that wiped the planet clean of most terrestrial life 66 million years ago.
Nearly nine out of 10 of the amphibian species are descended from just three lineages that survived the mass extinction.
Each of them jumped forward precisely at the junction of the Cretaceous and Paleogene periods – formerly known as the KT boundary – when the disaster happened.
The first survivors may have ridden out the meteor strike by burrowing underground, the scientists believe. Thereafter, it was arboreal tree frogs that led the way by exploiting newly available habitat niches.
Previous research had suggested that frog evolution took off 35 million years earlier and had nothing to do with the dinosaur apocalypse.
Study co-author Professor David Hillis, from the University of Texas at Austin, US, said: "We know that the mass extinction event wiped out most of the dinosaurs, except for a few bird species, which then exploded in diversity and became one of the dominant groups of land animals.
"As we look at more and more groups of life, we see the same pattern, and that turns out to be the case for frogs as well."
US colleague Professor David Wake, from the University of California at Berkeley, said a key factor in early frog success was the way the creatures adapted to living in trees as flowering plants spread across the planet.
"Frogs started becoming arboreal," he said. "It was the arboreality that led to the great radiation in South America in particular."
Trees are an ideal habitat for frogs not only because they provide a refuge from terrestrial predators, leaf cover on the ground, and abundant insects for food, said the researchers whose findings are reported in the journal Proceedings of the National Academy of Sciences.
American and Chinese scientists made the discovery after analysing genetic data from frogs within 44 living families.
Today’s frogs comprising more than 6,700 known species, are increasingly threatened by habitat destruction, increasing human population, and climate change.
Prof Wake added: "These frogs made it through on luck, perhaps because they were either underground or could stay underground for long periods of time.
"This certainly draws renewed attention to the positive aspects of mass extinctions: They provide ecological opportunity for new things. Just wait for the next grand extinction and life will take off again. In which direction it will take off, you don’t know."