New theory suggests salamanders relocated 25,000 kilometres from America to Asia

November 27th, 2007 - 4:20 pm ICT by admin  

London, Nov 27 (ANI): A new research on the history of ancient amphibians has indicated that salamanders once relocated almost 25,000 kilometres from America to Asia.
The plethodontidae salamander family contains about 380 species, 98% of which live in the Americas. The other 2% live in Europe and Korea, and no one knew how they got there.
“Though distributions like this are common amongst fast-travelling birds and mammals, but how salamanders managed something like this has been one of the big biogeographic mysteries of the past hundred years”, says David Vieites, an author of the new study.
The mystery started to unravel four years ago when Vieites and his colleagues went to Korea to study the newly-discovered and only-known Asian plethodontid, Karsenia koreana 1.
Karsenia was found to be closely related to a genus called Hydromantes , found in both California and Europe. But it was different enough to merit a new genus name, and to indicate a long period of independent evolution.
The most likely explanation seemed to be that a North American salamander lineage had travelled from America to Asia millions of years ago.
Such a journey seemed rather improbable, so Vieites and a team of biologists at the University of California, Berkeley, sequenced DNA from three key genes in 43 plethodontid species to work out whether this evolutionary story was correct.
The research team confirmed that Karsenia is a descendant of North American species 2. they also added information about its sideways relationships to European species and Hydromantes in California, that indicates that the latter two ’sister’ lineages both arose originally in Asia.
Together these data suggest that salamanders travelled from America to Asia in the late Cretaceous (some 80 million years ago), and then some of them went back again at the Paleocene/Eocene boundary (some 55 million years ago).
Although salamanders are amphibious, they do not swim in salt water, making ocean crossing impossible. This leaves the Bering land bridge, which has periodically connected Alaska and Siberia, as the easiest travelling route for these stubby-legged animals. The bridge has emerged and submerged many times in the past hundred million years and was above sea level when Karsenia evolved.
It is, however, odd for temperate-dwelling salamanders to be so far north as the Bering land bridge.
“Global warming was probably behind this intrepid journey,” David Wake, an author on the study, told Nature News. “A warm spell probably forced salamanders to move northwards to remain in comfortable temperatures, he explains, leading them to the bridge. Why they bothered crossing it is unknown,” he added. (ANI)

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