The extinction of the dinosaurs 66 million years ago may have had a startling effect on the population of frogs. Namely, it allowed them to explode, with three new lineages appearing.
A study describing these findings is published this week in the Proceedings of the National Academy of Sciences. The research was led by Sun Yat-Sen University in China, and supported by a number of US universities.
Using fossil records, they pieced together genetic differences in frog lineages, and observed how they diverged from each other. They found that the three major lineages of modern frogs arose almost simultaneously at the moment the dinosaurs were wiped out, able to make new niches for themselves on the less populated Earth.
"We think there were massive alterations of ecosystems at that time, including widespread destruction of forests," said study co-author David Blackburn from the University of Florida in a statement. "But frogs are pretty good at eking out a living in microhabitats, and as forests and tropical ecosystems rebounded, they quickly took advantage of those new ecological opportunities."
While frogs actually date back about 200 million years, it seems the end of the Cretaceous Period and the start of the Paleogene allowed frogs to massively diversify. Key moments in the tree of life of other animals, including birds or mammals, show a similar divergence as a result of climatic or geologic events.
Frogs were able to become one of the most diverse groups of vertebrates in the process, with more than 6,700 species known of today. While the dinosaurs and other animals perished after Chicxulub, this research shows just how hardy frogs are.
It also helps answer the quandary that many frog species around the world closely resemble each other, from Central Africa to Ecuador. They may have last shared a common ancestor 120 million years ago, before the Chicxulub impact that wiped out 75 percent of plant and animal life on Earth.
The global distribution of frogs goes back to the breakup of the supercontinent Pangea. It’s thought that frogs then used a relatively ice-free Antarctica to make the trek from South America to Australia.
It wasn’t good news for all frogs 66 million years ago, though. Many frog lineages, particularly in North America, were likely wiped out, meaning most frogs found in North America today arose after the age of the dinosaurs.
"If you could travel back to the time of T. rex in North America, there would be frogs, but the chorus you would hear at night would have been nothing like you'd hear today,” said Blackburn. “They're not even the same families."
