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Chillin’. Frogs can evolve along with changing pond temperatures, suggesting that climate change may not be their death knell.

Frogs Not Croaking Quite Yet

How great is the threat of climate change to biodiversity? Recent estimates based on computer modeling predict that one-third of all species could be driven extinct by 2050 (ScienceNOW, 7 January). But this approach ignores the possibility that species may evolve rapidly in response to a changing climate. Now there's some of the first concrete evidence that animals can rapidly evolve when the mercury's rising.

Yale ecologist David Skelly and colleagues studied how wood frogs in northeast Connecticut have responded to over 30 years of local climate change. In some areas, beavers have felled the trees that shade ponds. Other ponds have become shadier because people planted trees around them.

The group took a total of 150 tadpoles from ponds with various amounts of tree cover, then examined them in the lab for a suite of traits. The checklist included how well they tolerate high heat, how fast they develop at a given temperature, and what temperatures they prefer. The environment makes a big difference: For example, eggs taken from shady, cooler ponds produce tadpoles that develop faster than tadpoles from warmer ponds. They also actively seek warmer water, the team reports in the May issue of Ecology Letters.

These patterns show that frogs--often considered to be "coal-mine canaries"--can rapidly evolve new behaviors over short periods, says Skelly. He's quick to add that this doesn't imply that climate change is not a concern. But the finding highlights the importance of determining which species can rapidly adapt and under what conditions they can do it, to get a more realistic picture of the effects of climate change and to target ecological efforts more effectively.

Evolutionary ecologist Andrew Hendry of McGill University in Montreal, Canada, agrees that ignoring evolution may inflate estimates of extinction rates caused by climate change. ”But even though some populations seem able to adapt to climate change, this does not mean that evolution will save all species,” he says.

Related sites
David Skelly's Web site
Andrew Hendry's Web site