Carey James Balboa/Wikimedia Commons

Extinction that killed the dinosaurs may have led to frog explosion

The ancestors of this red-eyed tree frog (Agalychnis callidryas) may have gotten their big break thanks to the same mass extinction that wiped out the dinosaurs. In the wake of that event some 66 million years ago, which marks the end of the Cretaceous period and the start of the Paleogene, frog species underwent rapid diversification. To better understand how frogs evolved, scientists created a new phylogenetic tree—a branching diagram of evolutionary relationships—using data from hundreds of frog genomes. From this, they examined rates and patterns of diversification of species and discovered that most modern frog groups didn’t originate in the Mesozoic, as once thought. Instead, some 88% of living frog species—including all tree frogs—came from three main lineages that arose around the time of the Cretaceous-Paleogene extinction event, they report online today in the Proceedings of the National Academy of Sciences. Like many species that flourished after the dinosaurs, these frogs may have opportunistically occupied ecological niches suddenly left vacant. And tree frogs in particular may have benefited from the massive loss of vegetation and subsequent rebounding of forests on the planet.