Genetic Diversity of Microsatellite DNA Loci of Tibetan Antelope(Chiru,Pantholops hodgsonii)in Hoh Xil National Nature Reserve,Qinghai,China

The Tibetan antelope （Pantholops hodgsonii）, indigenous to China, became an endangered species because of considerable reduction both in number and distribution during the 20th century. Presently, it is listed as an Appendix Ⅰ species by CITES and as Category I by the Key Protected Wildlife List of China. Understanding the genetic diversity and population structure of the Tibetan antelope is significant for the development of effective conservation plans that will ensure the recovery and future persistence of this species. Twenty-five microsatellites were selected to obtain loci with sufficient levels of polymorphism that can provide information for the analysis of population structure. Among the 25 loci that were examined, nine of them showed high levels of genetic diversity. The nine variable loci （MCM38, MNS64, IOBT395, MCMAL TGLA68, BM1329, BMSI341, BM3501, and MB066） were used to examine the genetic diversity of the Tibetan antelope （n = 75） in Hoh Xil National Nature Reserve（HXNNR）, Qinghai, China. The results obtained by estimating the number of population suggested that all the 75 Tibetan antelope samples were from the same population. The mean number of alleles per locus was 9.4 ± 0.5300 （range, 7-12） and the mean effective number of alleles was 6.519± 0.5271 （range, 4.676-9.169）. The observed mean and expected heterozygosity were 0.844 ± 0.0133 （range, 0.791-0.897） and 0.838 ± 0.0132 （range, 0.786-0.891）, respectively. Mean Polymorphism Information Content （PIC） was 0.818 ± 0.0158 （range, 0.753-0.881）. The value of Fixation index （Fis） ranged from -0.269 to -0.097 with the mean of -0.163 ± 0.0197. Mean Shannon＇s information index was 1.990 ± 0.0719 among nine loci （range, 1.660-2.315）. These results provide baseline data for the evaluation of the level of genetic variation in Tibetan antelope, which will be important for the development of conservation strategies in future.

The Tibetan Antelope

Editor＇s note： Due to its broad territory and diverse natural environment, China is home to the widest range of wildlife species with 6,266 kinds of vertebrates, including 2,404 kinds of terrestrial animals and 3,862 kinds offish, which make up nearly lO percent of the world＇s vertebrates. The giant panda, the snub-nosed monkey, the South China tiger, the brown-eared pheasant, the red-crowned crane, the crested ibis, the white-flag dolphin, and the Chinese alligator are some of China＇s rare species of wild animals. This year, we have created a column to introduce some of these animals.

A Mitochondrial Genome Sequence of the Tibetan Antelope(Pantholops hodgsonii)

To investigate genetic mechanisms of high altitude adaptations of native mammals on the Tibetan Plateau, we compared mitochondrial sequences of the endangered Pantholops hodgsonii with its lowland distant relatives Ovis ames and Capra hircus, as well as other mammals. The complete mitochondrial genome of P. hodgsonii （16,498 bp） revealed a similar gene order as of other mammals. Because of tandem duplications, the control region of P. hodgsonii mitochondrial genome is shorter than those of O. ames and C. hircus, but longer than those of Bos species. Phylogenetic analysis based on alignments of the entire cytochrome b genes suggested that P. hodgsonii is more closely related to O. ames and C. hircus, rather than to species of the Antilopinae subfamily. The estimated divergence time between P. hodgsonii and O. ames is about 2.25 million years ago. Eutther analysis on natural selection indicated that the COXI （cytochrome c oxidase subunit I） gene was under positive selection in P. hodgsonii and Bos grunniens. Considering the same climates and environments shared by these two mammalian species, we proposed that the mitochondrial COXI gene is probably relevant for these native mammals to adapt the high altitude environment unique to the Tibetan Plateau.

The roles of calving migration and climate change in the formation of the weak genetic structure in the Tibetan antelope(Pantholops hodgsonii)

Geographical barriers and distance can reduce gene exchange among animals,resulting in genetic divergence of geographically isolated populations.The Tibetan antelope(Pantholops hodgsonii)has a geographical range of approximately 1600 km across the Qinghai-Tibet Plateau,which comprises a series of tall mountains and big rivers.However,previous studies indicate that there is little genetic differentiation among their geographical­ly delineated populations.To better understand the genetic structure of P.hodgsonii populations,we collected 145 samples from the 3 major calving regions,taking into consideration their various calving grounds and mi­gration routes.We used a combination of mitochondrial sequences(Cyt b,ATPase,D-loop and COX I)to inves­tigate the genetic structure and the evolutionary divergence of the populations.Significant,albeit weak,genetic differentiation was detected among the 3 geographical populations.Analysis of the genetic divergence process revealed that the animals gradually entered a period of rapid genetic differentiation approximately 60000 years ago.The calving migration of P.hodgsonii cannot be the main cause of their weak genetic structure because this cannot fully homogenize the genetic pool.Instead,the geological and climatic events as well as the coupling vegetation succession process during this period have been suggested to greatly contribute to the genetic struc­ture and the expansion of genetic diversity.