Say some bozo leaves his expensive watch lying next to a deck chair at the swimming pool where you work. You pick it up and ask around — nobody knows who it belongs to. It sits in Lost & Found for a month or two, and finally you just put it on and start wearing it. Someone else's misfortune benefits you. This happens in evolution, too. When one organism vacates an ecological niche, another one will slip right in there while the seat's still warm.
A new study published in the journal Proceedings of the National Academy of Sciences finds that 90 percent of frog species alive today descended from just three frog lineages that survived the Cretaceous-Tertiary mass extinction — also known as the K-T extinction event — that killed all nonavian dinosaurs 66 million years ago. The Earth was suddenly sort of empty, and the frog ancestors were like, "This rules!" And so they got busy making more frogs, evolving over millennia, and filling in as many niches as they could.
"We think the world was quite impoverished as a result of the K-T [extinction] event, and when the vegetation came back, angiosperms dominated. That's when trees evolved to their full flowering," says coauthor David Wake, a University of California, Berkeley professor and a curator of the Museum of Vertebrate Zoology, in a press release. (Angiosperms are flowering plants.) "Frogs started becoming arboreal. It was the arboreality that led to the great radiation in South America in particular."
Wake and his coauthors examined 95 genes from 44 of the world's 55 frog families. They found that even though the three main frog lineages emerged about 35 million years before the mass extinction, the frogs really hit their stride once all those pesky dinos were out of the picture.
Frog ancestors were thus unimpeded by approximately 80 percent of the animals that had existed (the same could be said for our ancient mammalian ancestors). They not only spread out to the far corners of the world, the ancient frogs learned neat new tricks that have helped them in the long run. For instance, they developed the ability to conduct all their business in trees, giving them greater protection. They also evolved a method for laying eggs on land, rather than in the water.
"These frogs made it through on luck, perhaps because they were either underground or could stay underground for long periods of time," Wake said. "This certainly draws renewed attention to the positive aspects of mass extinctions: They provide ecological opportunity for new things. Just wait for the next grand extinction and life will take off again. In which direction it will take off, you don't know."
The history of evolution's written by the survivors.