CHANGSHA, March 17 (Xinhua) -- Chinese scientists identified seven major clades of critically-endangered wild Chinese giant salamander in China, with three clades inhabiting Hunan's Zhangjiajie, a major origin area of the world's existing largest amphibian.

The paper, published online in the journal Ecology and Evolution, depicts a relatively-intact distribution map of Chinese giant salamander's clades in natural species range and suggests that the release of giant salamanders back into the wild should match their genetic differences.

A total of 320 wild samples were collected from 33 localities covering the most of its native distribution range of giant salamanders. Seven clades were determined in the study, based on wide geographic sampling as well as sequence alignment of mitochondrial DNA and nuclear DNA.

The paper's first author Liang Zhiqiang, an associate researcher at the Hunan Fisheries Science Institute, said that the study filled the gaps in the genetic diversity of wild giant salamanders in six provinces, including Hunan and Jiangxi, and provides much-needed genetic background information for the conservation of wild giant salamanders in these provinces.

"It is rare that there are three clades in one single area and the finding can help improve monitoring programs and develop conservation strategies for the species in Zhangjiajie," Liang said.

"Although the release of captive-reared individuals into the wild could have a positive effect on giant salamanders, negative effects are also possible. For instance, the introduction of individuals with non-native genotypes might lead to loss of local adaptations and native genetic variability.

"Genetic testing is needed before releasing giant salamanders into the wild to ensure that they are part of the local clades," Liang said.

Since 2002, the National Giant Salamander Nature Reserve of Zhangjiajie, of central China's Hunan Province, has released more than 20,000 farm-reared baby salamanders into the wild. Microchips are implanted under the skin of the released salamanders to record information such as gender and breeding time, and to establish their genetic files.

"The chips are equivalent to the ID cards of the giant salamanders, which can find matches in the gene storehouse to help guarantee genetic purity of the local wild giant salamander population," said Deng Zhiyong, head of the protection section in the reserve.