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Salamanders hot-footed it to Asia long ago, study says

December 01, 2007|Karen Kaplan | Times Staff Writer

Go west, young salamander!

New genetic evidence suggests ancient amphibians heeded this advice, migrating from the West Coast of North America to Asia via a land bridge connecting Alaska and Siberia about 80 million years ago.

The analysis, published this week in Proceedings of the National Academy of Sciences, explains how small colonies of so-called lungless salamanders wound up in Italy and Korea when 98% of the species live in the Western Hemisphere.

Researchers from UC Berkeley and Seoul National University examined DNA from 43 salamander species to build a family tree. By comparing the same three genes in each species, they were able to tell which were close cousins and which were distant relatives.

Knowing how long it took for mutations to occur, they also estimated when each species arose.

They concluded that the family of lungless salamanders -- which breathe through their skin and account for two-thirds of all salamander species -- originated in North America 180 million years ago during the Jurassic period, when dinosaurs roamed.

About 100 million years later, as global temperatures rose during the late Cretaceous period, West Coast salamanders began spreading north in search of hospitable climates. Over 10 million to 15 million years, they made it to what is now the Bering Sea and continued moving into eastern Asia.

The intercontinental migration is particularly impressive considering that a typical salamander never strays outside a territory measuring 250 to 300 square feet, said lead author David Vieites, a postdoctoral researcher at UC Berkeley's Museum of Vertebrate Zoology.

Some of the Asian salamanders headed farther west to Europe when the climate warmed again 40 million to 50 million years ago. Others trekked back to North America.

Global temperatures are rising again, but this time it's happening so fast that the salamanders are vulnerable, Vieites said.


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