Salamanders show Americas joined much earlier than thought

by PHENOMENICA on MARCH 20, 2013

The humble salamander may provide evidence to support a controversial claim that the continents of North and South America were joined together much earlier than previously thought, scientists say.

The two continents are generally believed to have been joined together around three million years ago by the formation of a land bridge what is now Panama that sealed up the sea channel between them.

However, a new study of salamanders in South America by Dr Kathryn Elmer of the University of Glasgow, has found evidence that challenges these assumptions and supports a controversial claim by Smithsonian scientist Carlos Jaramillo that most of the Isthmus of Panama was formed around 23 million years ago.

The fusion of both land masses led to a two-way migration of animals called the ‘Great American Biotic Interchange’, where animals that had previously evolved separately moved between the two continents, increasing the biodiversity in both regions.

The relative dearth of species of salamander in South America around 30 compared to Central America, where there are more than 300 species, is usually attributed to the relatively short time the tiny lizard-like amphibians have had to make their way south down the Isthmus of Panama.

However, using DNA analysis, Elmer found that salamanders in South America had much greater genetic divergence from their Central American cousins than should be expected if salamanders migrated across a three million year-old land bridge.

Read on:  http://www.phenomenica.com/2013/03/salamanders-show-americas-joined-much-earlier-than-thought.html