Scientists have revealed through a study published in Proceedings of the National Academy of Sciences that the mass extinction event that wiped out three-fourths of life on Earth including dinosaurs paved way for the swift rise of frogs.
In the study scientists have put forward a new tree of life for frogs that they claim not only helps solve longstanding riddles about relationships of frogs, but also sheds light on the history and pace of frog evolution.
Researchers at Florida Museum of Natural History on the University of Florida campus point out that while frogs have been around even during the age of dinosaurs, diversity in the species wasn’t all that high. It was only after the extinction of the dinosaurs that there was a huge burst in diversity that resulted in the vast majority of frogs we see today. Scientists found that about 88 per cent of living species of frogs that we see toay appeared simultaneously, evolving on the heels of the extinction event.
Frogs rose to become one of the most diverse groups of vertebrates, with more than 6,700 described species. But sparse genetic data has hindered scientists from reliably tracing their evolutionary history and the links between frog families.
For the study researchers at the Florida Museum joined hands with their those from Sun Yat-Sen University, the University of Texas at Austin and the University of California, Berkeley. Scientists tackled the mystery of frog evolution with a dataset seven times larger than that used in prior research. The team sampled a core set of 95 nuclear genes from 156 frog species, combining this with previously published genetic data on an additional 145 species to produce the strongest-supported evolutionary tree, or phylogeny, to date. The tree represents all 55 known families of frogs and generates a new timeline of frog evolution.
The researchers then used fossil records to translate genetic differences between frog lineages into dates at which they likely diverged from one another. When the analyses pointed to a simultaneous evolution of the three major frog clades — Hyloidea, Microhylidae and Natatanura — the researchers initially eyed the finding with skepticism, said Peng Zhang, a corresponding study author and professor in the department of biochemistry and molecular biology at Sun Yat-Sen University in China.
The study also indicates that global frog distribution tracks the breakup of the supercontinents, beginning with Pangea about 200 million years ago and then, Gondwana, which split into South America and Africa. The data suggests frogs likely used Antarctica, not yet encased in ice sheets, as a stepping stone from South America to Australia.