A new study has revealed that after the asteroid strike that killed off all the dinosaurs on Earth millions of years ago, frogs got a huge leap for the frogs that colonized the planet. The study published on Monday shows how frogs became from the underwater amphibian on the corner of the ecosystem to one of the most diverse vertebrates in the world just after the dinosaurs came to an extinct.
The report published in the Proceedings of the National Academy of Sciences says that more than 10 species of frogs survived the mass extinction which wiped out three quarters of the life on Earth some 66 million years ago. Among them, only three major types of frogs continued to diversify and started populating the planet and today we know about 6,700 species of them. The rest of them eventually died out or mixed up with the other species to create new ones.
Almost 9 out of 10, or 88 percent of today’s frogs can be traced back to their three lineage of hardy ancestors. “Frogs have been around for well over 200 million years, but this study shows it wasn’t until the extinction of the dinosaurs that we had this burst of frog diversity that resulted in the vast majority of frogs we see today,” said study co-author David Blackburn, associate curator of amphibians and reptiles at the Florida Museum of Natural History. “This finding was totally unexpected,” he added.
Before this revelation, it was believed that most modern frogs continued their lifespan and evolution at a steady pace since some time between 66 to 150 million years ago.
But the study revealed that frogs made a dramatic entrance into the scene almost like an “explosion” and took over the habitats abandoned by the big bones.
This happens to be the largest genetic study till date. The researchers in China and the United States compiled the largest set of frog genetic data ever evaluated to run the study, where they took samples from 156 species of the little amphibians and and combined them with previously recorded data on 145 more species. Past studies looked at five to 12 genes, while the current one examined variations in 95 genes, offering a much more detailed look at how individual species relate to one another. They also studied fossils to determine exactly when different types of frogs started emerging from their previous species.
Researchers found “evidence of not one but three explosions of new frog species, on different continents, and all concentrated in the aftermath of the mass die-off of most dinosaurs and many other species about 66 million years ago,” said the report.
Of these three surviving lineages, Microhylidae and Natatanura came from Africa. And the third, Hyloidea started spreading throughout what we know today as South America.
“These frogs made it through on luck, perhaps because they were either underground or could stay underground for long periods of time,” said co-author David Wake of the University of California.
“This certainly draws renewed attention to the positive aspects of mass extinctions: They provide ecological opportunity for new things,” he added.
David Hillis, co-author of the study and professor integrative biology at University of Texas, Austin believes that the same happened with birds. “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.”, he said.
The frogs found new habitats and evolved to adjust into them. Some climbed on trees and became tree frogs. “We think there were massive alterations of ecosystems at that time, including widespread destruction of forests,” said Blackburn.
“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.”
“I think the most exciting thing about our study is that we show that frogs are such a strong animal group,” said lead author Peng Zhang, a researcher at Sun Yat-sen University in Guangzhou, China.