Using frogs collected by Che and others, including frogs collected 20 years ago in Tibet and the Himalayas by Theodore Papenfuss, a herpetologist in UC Berkeley's Museum of Vertebrate Zoology, the researchers analyzed four genes from the nucleus in 29 individuals from 24 species of spiny frog. The analysis showed the Paini is composed of two major groups and five distinct lineages, which was a surprise, Wake said.
"The study has revealed at least five unnamed frogs in Indochina and adjacent Yunnan Province in China," Papenfuss said.
According to the researchers' genetic reconstruction, the tribe Paini arose in what is now Indochina and spread into Western China about 27 million years ago, diverging into two groups: Nanorana, now consisting primarily of high-elevation species up to 4,700 meters, in Western China; and Quasipaa, consisting of mostly low-elevation species in Indochina and South China.
As the Tibetan plateau was pushed higher, it became separated from the Himalayas, isolating populations in these regions some 19 million years ago. Those restricted to the Himalayas are now considered the Paa subgenus. The Nanorana subgenus isolated in Tibet began to diversify again about 9 million years ago, consistent with the period during which the Tibetan plateau rose above 3,000 meters. These new Nanorana species became well adapted to the cold, arid, low-oxygen conditions of Tibet, and as a result, some organs degenerated, Papenfuss said. For example, some frogs today have no or reduced structures in the ear, including the external tympanum, which transmits sound to the inner ear, and the columella in the middle ear.
The researchers found that in Indochina and South China, on the other hand, the Quasipaa frogs were split by the uplift of the Truong Son Mountain Rang
|Contact: Robert Sanders|
University of California - Berkeley