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DISCOVERIES

Central American frogs cousins of those found in South America, DNA reveals

EVOLUTION
Many of the frogs hopping around Central America and the Caribbean islands were once castaways from South America that sailed hundreds of miles to their new homes on rafts, according to new research. For years, scientists have debated the evolutionary history of the eleutherodactyline frogs, which breed on land and lay eggs that hatch fully formed offspring rather than tadpoles, but many agreed the frogs were too fragile to make such a long trip over salt water on mats of vegetation. Yet when Pennsylvania State University evolutionary biologist S. Blair Hedges and his colleagues compared the DNA of about 280 species of this frog, building a family tree and estimating how much the DNA might have changed over time, they discovered that the South American frogs must have arrived in Central America and the Caribbean sometime between 29 million and 47 million years ago long after there were any land bridges connecting the regions. The frogs must have drifted by sea, says Hedges, in much the same way that many animals in Hawaii and the Galapagos got to their islands. "They dispersed naturally, riding on rafts called 'flotsam,' which are usually debris washed out during a storm, like hurricanes or a big thunderstorm," he said. "In the water, the frogs wouldn't have survived. The salt water dries them up, so they definitely weren't swimming."

BOTTOM LINE: Geography strongly influences evolution. The eleutherodactyline frogs of South America, Central America, and the Caribbean are part of the same family tree and share a single common ancestor, which most likely migrated over water rather than land.

CAUTIONS: While the study was large, it included only a small fraction of South American species, so there's the potential for more surprises in the future.

WHAT'S NEXT: Hedges will try to figure out how the frogs traveled among Caribbean islands and how, for example, those on Cuba are related to those on Hispaniola.

WHERE TO FIND IT: Proceedings of the National Academy of Sciences, June 12

HEATHER WAX

DIABETES

Drug appears to combat unhealthy eating as well as genetics


Researchers from Harvard and the pharmaceutical company Bristol-Meyers Squibb have developed a drug that prevents and reduce symptoms of diabetes and clogged arteries in mice. In a new study, they tested the drug on mice fed a high-fat diet and on others genetically susceptible to diabetes or clogged arteries. Both groups of mice remained healthier than mice that didn't get the drug. The treatment is designed to block the action of a protein called aP2 that triggers harmful reactions when fatty foods are eaten. The researchers, led by Gokhan Hotamisligil at the Harvard School of Public Health, had previously discovered that the protein has a similar effect in people.

BOTTOM LINE: "This is one intervention that can be used to treat two major diseases -- diabetes and atherosclerosis," said Hotamisligil.

CAUTIONS: The study did not look into all the potential toxic effects of the drug nor was it tested on humans. Also, some of the researchers work for Bristol-Meyers Squibb, which makes the drug.

WHAT'S NEXT: Researchers want to test the drug for effectiveness and side effects in humans.

WHERE TO FIND IT: Nature, June 7

SENA DESAI GOPAL

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