Studies On Conservation Genetics Of The Giant Panda

The global population of giant pandas was estimated to be -1000 and currently restricted to the isolated Qinling, Minshan, Qionglai, Daxiangling, Xiaoxiangling and Liangshan mountain ranges on the edge of the Tibetan plateau. Much effort has been expended on conservation of the species. Considerable knowledge has been gathered regarding the physiology, ecology, biochemistry, and anatomy of giant pandas, but little is know about the genetic background of wild animals, which may be an important element of a conservation strategy. Conservation genetics is able to reveal the origins and evolutionary histories of species/subspecies, the relationships within and between populations of species and the genetic diversity of groups of animals, and can thus define priorities of conservation units and effective conservation plans.The small size of the wild population results in inbreeding, causing loss of polymorphic loci and higher homozygosity in descendants. For this reason, appropriate markers and large sample sizes are essential for reliable detection of genetic patterns in pandas. Previous studies revealed that mitochondria! DNA and microsatellites did not provide insufficient data for genetic analyses of giant pandas. Therefore, DNA fingerprinting is more suitable for the giant panda because it is capable of revealing whole genome polymorphism patterns. Furthermore, the probes used in DNA fingerprinting, variable number tandem repeat (VNTR) families, change at a rate of 100-1000 times fester than conventional alleles and can thus reflect more recent historic events. Bamboo die-off during 1975-1985 caused the death of several hundred giant pandas. Most of these carcasses were preserved by formalin fixation, but the material was not used for genetic study because cross-linking between proteins and DNA makes extraction of high-quality nucleic acid squences problematic.This study is designed to (1) develop reliable methods to extract high-quality DNA from formalin-fixed tissues and a new probe, which possesses the highest probability in the paternity testing and is suitable for identifying the homozygous loci; (2) to use DNA fingerprinting and historical samples to detect population structure, genetic differentiation and population history of giant pandas; (3) to advise conservation strategies using the analyses of conservation genetics. All results could be summaried as follows.(1) Although gradual dehydration is helpful for DNA extraction from fixed tissues but it can not give high molecular weight DNA due to incomplete formalin removal. However, combining with critical-point drying, the gradual dehydration can result in the extraction of high molecular weight DNA, which is identical to the size of genomic DNA from fresh liver, because critical temperature and critical pressure can remove foramlin completely. Thus, the quantity and quality of DNA from fixed tissues is reliable and can be applied for molecular genetic studies, phylogenetic relationship analysis, forensic DNA detection and retrospective clinicogenetic analysis.(2) The new probe, gp2000, had the highest paternity probability and succeeded in identifying the homozygotic genes and discriminating giant panda individuals. It produced up to 39 informative loci in single giant panda and two species/subspecies-specific bands, and thus represents the best opportunity for the detection of genetic diversity and genetic differentiation of giant pandas.(3) The two largest populations, Minshan and Qionglai, had the highest level of genetic diversity and the two smallest populations, Daxiangling and Xiaoxiangling, had thelowest level of heterzygosity, indicative of serious inbreeding in the Daxiangling and Xiaoxiangling populations. The Qinling population possessed smaller size than that of the Minshan and Qionglai populations and had the fewest bands and the narrowest range of band distribution. However, the Qinling pandas showed similar genetic variability to the Minshan and Qionglai populations, suggesting that f...