New study contradicts assumption that true frogs diversified as they expanded their range around globe

phys.org | 9/13/2017 | Staff
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Evolutionary biologists long have supposed that when species colonize new geographic regions they often develop new traits and adaptations to deal with their fresh surroundings. They branch from their ancestors and multiply in numbers of species.

Apparently, this isn't the story of "true frogs." The frog family scientists call Ranidae are found nearly everywhere in the world, and their family includes familiar amphibians like the American Bullfrog and the European common frog.

New - Research - University - Kansas - Royal

New research from the University of Kansas appearing in Royal Society Biology Letters shows, in contrast to expectations, "the rapid global range expansion of true frogs was not associated with increased net-diversification."

"First, we had to identify where these true frogs came from and when they started their dispersal all over the world," said lead author Chan Kin Onn, a doctoral student at KU's Biodiversity Institute. "We found a distinct pattern. The origin of these frogs was Indochina—on the map today, it's most of mainland Asia, including Thailand, Vietnam, Cambodia and Burma. True frogs dispersed throughout every continent except Antarctica from there. That's not a new idea. But we found that a lot of this dispersal happened during a short period of time—it was during the late Eocene, about 40 million years ago. That hadn't really been identified, until now."

Chan - Rafe - Brown - Curator-in-charge - KU

Next, Chan and co-author Rafe Brown, curator-in-charge of the KU Biodiversity Institute's Herpetology Division, looked to see if this rapid dispersal of true frogs worldwide triggered a matching eruption of speciation.

"That was our expectation," Chan said. "We thought they'd take off into all this new habitat and resources, with no competition—and boom, you'd have a lot of new species. But we found the exact opposite was true. In most of the groups, nothing happened. There was no increase in speciation. In one of the groups, diversification significantly slowed down. That was the...
(Excerpt) Read more at: phys.org
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