大鲵洞穴种群的保护遗传学研究

The Chinese giant salamander (Andrias davidianus) is the world's largest amphibian and contains a long and distinct evolution history. It has remained nearly unchanged for millions of years and is thought to have occurred throughout Eurasia. Its current distribution, however, is highly fragmented and nearly all wild individuals exist inside mountain caves inaccessible to people. This species has experienced dramatic population declines, estimated to be as much as 80% over the last three generations due to over-exploitation. To this end, it is now listed as critically endangered. Wild populations are continuing to decline despite increased attention from the Chinese government and international organizations. The conservation of Chinese giant salamanders is especially difficult as it faces not only environmental problems but also the illegal harvesting and constant translocations..It is listed as national protected animals since 1970s whereas the law enforcement and protection is hampered by the lack of information on its genetic structure among the large watersheds of Pearl, Yangtze and Yellow Rivers. To compound the rampant, illegal collection of wild adults and larvae, the government routinely organizes releasing activities of captive-bred individuals without regard to local genetic signatures. The individuals that were fled from farms may have changed the purity of some original populations. Moreover, the huge south-north water diversion project will change the gene flow of Chinese giant salamander..In this study, we will focus on the wild populations that exists in karst caves, to identify the haplotypes of the mitochondrial (D-loop and Cytb) and nuclear genes (major histocompatibility complex markers and microsatellites) in disable larvae that flush from the mountain caves, to assess the genetic diversity and structure and develop spatial-specific barcode of Chinese giant salamander. This will compensate the shortcomings of human relocation, small sample size and insufficient genetic makers in past researches, and provide guidelines for the classification of conservation management units, releasing plans, and selection of parental resources for farming.

大鲵是全世界最受关注的两栖动物之一，是黄河、长江、珠江三大河流生态系统保护和治理的旗舰物种。十年来政府耗费巨资开展增殖放流，然而原始种群却持续萎缩，栖息地破碎化严重，并面临遗传资源"污染"的风险，急需开展保护遗传学研究。现有的研究限于个体的放归与逃逸、样本量较少及遗传标记不足等因素，未能发现明显的遗传分化格局。本研究立足于受人为迁移个体影响最小的洞穴种群，在全国抽取21个有代表性的地理种群，采集岩洞中流出的幼苗样品，分型识别线粒体基因（D-loop、Cytb）和核基因（MHC、微卫星）等遗传标记，深入了解大鲵的遗传结构与地理分化，评估洞穴种群的适应潜力，为保护管理单元的划分、地区特异性遗传标记的建立及增殖放流的决策提供依据，同时为养殖场亲本的选育提供指导。

大鲵是两栖类动物的旗舰物种，是全世界最受关注的极危物种之一，也是我国重点保护的水生野生动物。长期以来，国内外多家单位倾注了很大的精力、财力进行研究和保护，然而原始种群持续萎缩，栖息地破碎化严重；相反，由于2007年仿生态繁殖模式的突破和农业部门的大力推广，至2015年5月，全国驯养繁殖的大鲵存有量已经超过1千万尾，养殖个体的迁移与人工放流现象严重，仅2010-2013年放流个体达9.2万尾，这可能很大程度上破坏了大鲵的原始遗传背景，物种命运岌岌可危。.本研究立足于受人为迁移个体影响最小的喀斯特洞穴种群，采集岩洞中流出的幼苗样品，运用多种遗传标记研究大鲵野生种群的遗传格局，揭示大鲵适应进化的遗传多样性基础。. 首先，抽取川渝13个有大鲵历史记录的县市，进行标准化的1公里样线的夜间潜水调查、20个陷阱调查和附近3个村庄的30位村民问卷调查，结果未发现1尾野生个体，在过去五年内，仅一半地区有野生个体发现，表明大鲵已从许多地区功能性灭绝。.其次，调查发现从喀斯特洞穴流出的幼苗在2010年前后被村民疯狂捕捞，大大影响了洞穴种群的补充量，一些洞穴已经不再流出幼苗；对洞穴中流出的幼苗遗传多样性进行模拟运算，提示有效种群大小介于9-25个，种群瓶颈效应明显，因此应当“多洞穴一体保护”。. 最后，分析发现秦岭、大巴山与武陵山区大鲵遗传背景的差异明显，应当划为不同的保护单元，已分别就研究结果给重庆市农业管理委员会和四川省水产渔政局提交大鲵资源保护与管理建议书，最终研究结果将以论文和著作的形式展现。