Frog evolution linked to dinosaur asteroid strike
A new analysis shows that frog populations have soared after the extinction event there are 66 million years.
It seems to contradict the previous evidence suggests a much earlier origin for many key groups of frogs.
The work of a team of researchers from the United States and China is described in PNAS.
Frogs have become one of the most diverse groups of vertebrates, with more than 6,700 species described. But the lack of genetic data has hampered efforts to track its evolutionary history.
The new study shows that the three main lineages of modern frogs – which together account for about 88% of live frog species – appear almost simultaneously.
Red Eye Tree LIBRARY frogImage copyrightSCIENCE PHOTO
The red-eyed frog comes from animals that have made the greatest resurgence of forest cover due to the impact of asteroids
This impressive diversification of species seems to have occurred in the heels of asteroids, which reached what is now the edge of the Yucatan peninsula in Mexico.
Releasing more than a billion more energy than a nuclear bomb, the impact of space has erased three quarters of all life on earth. But it also seems to have paved the way for the emergence of frogs.
The scientists took samples of a nucleus of 95 DNA genes from 156 species of frogs.
They then combined these data with the genetic information of 145 additional species to produce a “family” of detailed tree frogs, according to their genetic relationships.
Using fossil frogs to provide “true ground” genetic data, researchers were able to add a calendar for their family tree. The three largest groups of frogs – the Hyloidea the Microhylides and Natatanura – all have their origin in an expansion that occurred there after 66 million years.
“No one saw this result before,” said co-author Peng Zhang of Sun Yat-Sen University in Guangzhou, China.
“We have re-done the analysis using different parameters, but the result was still the same, I realized that the signal was very strong in our data, what I saw could not be an incorrect thing.”
Another author, David Blackburn, the Florida Museum of Natural History, said:
“Frogs were carried out for over 200 million years, but this study shows that it is only dinosaurs that we had this explosion of diversity of frogs that resulted in the vast majority of frogs we see today.”
Dr. Blackburn said the speed at which frogs were diversifying after impact suggests that survivors were probably filled with new ecological niches.
The Chicxulub event would have destroyed much of the vegetation on earth. But as forests have begun to recover after the event, frogs appear to have been one of the groups that have made most of the new habitats.
Researchers point out that none of the frog lineages that originated before extinction and survived through the impact of asteroids can not be adapted to tree life.
The toad (actually a frog) belongs to a minority of frogs whose lineages occurred before the extinction event
“All the roots of the tree (for example, in hyloïdes or natatanurans) after the event [the extinction of Chicxulub],” the authors wrote in their PNAS article.
This, according to them, “supports the hypothesis that mass extinction [Chicxulub] has shaped the present diversity of frogs.”
The study also shows that the global distribution of the frog after the dissolution of the supercontinent, from Pangea is about 200 million years, and Gondwana, which is divided into South America and Africa.
The data suggest that the frogs were probably using Antarctica, however, which is not integrated into the ice sheets, as a springboard for South American Australia.
“I think the most interesting thing about our study is that we show that frogs are such a powerful group of animals. They survived the mass extinction … which has completely killed the dinosaurs,” said Peng Zhang.
However, frogs – like other amphibians – face many challenges, including loss of habitat due to felling and diseases such as chytrid fungus and ranavirus.