Tracing the family tree of frogs has been something biologists have grappled with for some time. Examining fossils and studying limited genetic data was the only way researchers could try to put the pieces of the frog family tree together. By analyzing this data, scientists determined that most frog species popped up between 150 million to 66 million years ago, at a slow but steady pace. However, a new study shows a mass extinction that occurred 66 million years ago caused a surge of new frog species. The study findings were published in the journal Proceedings of the National Academy of Sciences.
Compiling the largest set of frog genetic data ever, scientists with the University of California, Berkeley, the Florida Museum of Natural History, The University of Texas at Austin, and Sun Yat-Sen University in China evaluated evolutionary relationships to prepare the most accurate frog family tree available to date. Evidence showed three different explosions of new frog species, all of which occurred during the aftermath of the mass extinction that took place approximately 66 million years ago.
Researchers believe the mass extinction wiped out most of the frog species of that time, leaving in its wake only a few survivors. With so many other animal species annihilated at the same time, researchers believe it left many new ecological niches for the remaining frogs to spread into, which helped them to diversify at a rapid pace.
During the study, researchers gathered and examined genetic samples from 156 different frog species. They then combined that information with 145 additional species from data that had been published previously in order to create the most complete frog family tree to date. Researchers analyzed variations in 95 different genes to get a better understanding of how different frog species relate to one another, compared to previous studies that only looked at 5 to 12 different genes.
Currently, there are over 6,700 documented frog species. These species represent 55 families of frogs that live in various habitats, including everything from tree dwellers, those that live underground, and those that make their homes in aquatic environments. Researchers believe this latest study gives a more pointed look at the specific timeframe in which frog diversity occurred.
By Trixie Dillwood