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Genetic Survey of Captive Pandas Indicates Overall Genetic Health, Suggests Breeding Strategies

NEW YORK (GenomeWeb) – Giant panda populations in breeding centers in China are largely genetically healthy, according to a genotyping analysis appearing in Molecular Biology and Evolution.

Researchers led by Fuwen Wei at the Chinese Academy of Science's Key Laboratory of Animal Ecology and Conservation Biology examined 19 microsatellite loci of 240 captive giant pandas, Ailuropoda melanoleuca, from four different breeding centers as well as mitochondrial DNA samples from 220 of those captive animals and from 245 previously studied wild pandas.

By comparing the various populations, Wei and colleagues found high levels of genetic diversity and low levels of inbreeding among the pandas.

They also, though, found genetic structures among the populations, with certain groups appearing to be more closely related.

"Using a large-scale genetic database we found that captive populations are genetically healthy and self-sustainable on the whole, as indicated by the ample genetic variation, low levels of inbreeding, and large captive population size," Wei and colleagues wrote in their paper. "This is an exciting result and rewarding of recent decades of captive breeding."

Giant panda are endangered, with an estimated 2,500 individuals living in the wild in six fragmented regions. More than 65 reserves have been established as well as breeding centers like those examined this this new study: the Chengdu Research Base of Giant Panda Breeding, China Research and Conservation Center for the Giant Panda at Wolong, and Shaanxi Rescue and Breeding Center for Rare Wildlife. The fourth captive population included in the study was from the Beijing Zoo.

These breeding programs, the authors said, have become increasingly successful and, as a result, there are plans to release captive-born pandas into the wild. The success of that plan, they noted, is contingent upon the captive populations being genetically healthy.

Based on their genotyping data, Wei and colleagues identified 26 polymorphic sites and 41 unique haplotypes, 17 of which were shared among the captive and wild populations. Both haplotype diversity levels and the mean number of alleles per locus were similar between wild and captive populations, indicating to the researchers that high-level genetic diversity was preserved in the captive populations.

Additionally, the researchers calculated the individual inbreeding and pairwise relatedness for the pandas, and found, as a whole, that inbreeding seems to be effectively managed.

Through Bayesian clustering analysis, the researchers found strong genetic structuring in the captive populations. Pandas from Louguantai and Chengdu formed one cluster while Wolong and BJ pandas formed another.

That clustering of Louguantai and Chengdu populations together is cause for some concern, the researchers noted.

The Louguantai population, they said, is supposed to represent the wild Qinling panda population, which diverged from non-Qinling populations some 300,000 years ago and then the separate groups underwent local adaptations, which is reflected by their different morphologies.

The Chengdu population, meanwhile, is derived from non-Qinling pandas from Minshan and Qionglai populations.

Thus, this clustering indicates a mixture of Qinling and non-Qinling wild populations.

"This exchange may disrupt patterns of local adaptation established over hundreds of thousands of years, and thus would result in an unpredictable impact on wild populations if captive individuals were reintroduced into their original environments," the researchers said.

They suggested that a Louguantai population with a pure Qinling source be managed independently of other pandas so that it reflects the genetic distinctiveness of the Qinling population.

In contrast, the researchers encouraged increased exchange between the non-clustering Chengdu and Wolong populations, as they represent only recently diverged panda populations, to increase genetic diversity.

"However, while the big picture is positive, our genetic survey reveals some important but previously cryptic problems in captive management, such as the poor genetic status of the [Louguantai] population and its exchange with [Chengdu]," and "the scant exchange between [Chengdu] and [Wolong]," Wei and colleagues said. "We hope that the issues and suggestions identified here enhance the captive giant panda population as this high-profile program transitions to releasing animals into the wild."