黑颈长尾雉线粒体DNA、微卫星及MHC Ⅱ类B基因多态性研究

Mrs Hume's Pheasant (Syrmaticus humiae), a near threatened species in IUCN list, inhibits fragmentizely in west-southern Guangxi province. Since 1970s, the population sizes have been declined sharply because of continuing habitat loss, habitat fragmentation and hunting under the influence of human activity. About 283 Hume's Pheasants were restocked in Cenwanglaoshan Nature Reserve in June 2003, to contain the number declining of pheasant. Now a stable population, with about 200 individuals, was established with stage victory. However, the population growthcan not improve effectively in genetic diversity level after bottleneck effect. To date, the protection of the pheasant does not base on genetic background, which are blindness and not exactly scientific. In the present study, we will collect samples from the three populations, captive, reestablished, and wild populations. To comprehensively focus on genetic diversity, we will use three genetic markers, mitochondrial DNA, microsatellites, and major histocompatibility complex (MHC), with both non-coding regions and functional loci. The present study may determine the feasibility of the population rejuvenation experienced severe bottleneck effect, and provide scientific and effective data for the establishment and conservation methods for Syrmaticus humiae. This project can provide insight into the protection strategy and action plans for most rare and endangered pheasants, and hopefully can be the demonstration radiation for other similar species or area in China.

黑颈长尾雉（Syrmaticus humiae）是国家Ⅰ级保护的珍稀濒危雉类。广西是该物种重要栖息地之一。由于栖息地丧失、破碎化、猎杀等人类活动影响，上世纪70年代以来种群数量急剧下降。为遏制种群数量进一步下降，2003年广西岑王老山国家级自然保护区开展了再引入研究，至今该保护区已经形成了约200只的稳定种群，再引入获得了阶段性成功。然而，经过严重瓶颈效应的物种种群数量的增长并不能带来遗传多样性水平的有效提升。黑颈长尾雉的保护是在缺乏遗传背景基础上展开的，具有很大的盲目性和非科学性。本研究采用中性分子标记（线粒体DNA和微卫星）和适应性分子标记（MHC基因）对人工圈养种群、再引入种群和野生种群的遗传多样性水平及种群结构进行较全面的评估。其目的是探讨经历严重瓶颈效应后濒危物种种群复壮的可行性，并提出科学有效的保护策略和行动计划，也为我国濒危雉类的保护提供借鉴和参考。

黑颈长尾雉（Syrmaticus humiae）是国家Ⅰ级保护的珍稀濒危雉类。广西是该物种重要栖息地之一，由于栖息地丧失、破碎化、猎杀等人类活动影响，上世纪70年代以来种群数量急剧下降。本研究采用中性分子标记（线粒体DNA和微卫星）和适应性分子标记（MHC基因）对人工圈养种群、再引入种群和野生种群的遗传多样性水平及种群结构进行较全面的评估。从贵州和广西两省共采集到73饿野外种群样品，主要分布在广西-贵州两省的南盘江和红水河流域的6县（隆林县、西林县、田林县、乐业县、天峨县和罗甸县）的4个黑颈长尾雉地理种群。通过线粒体DNA和微卫星分析结果表明，分布在贵州省和广西的野生黑颈长尾雉种群具有较高的遗传多样性，种群之间遗传分化很小，分化主要主要发生在种群内的个体之间，种群间基因流较大，种群间基因交流较大。线粒体DNA和微卫星DNA遗传标记共同分析结果表明，323国道对TLX和LX两个种群之间并没有产生阻隔效应，南盘江和红水河在LX和LD、LX和PJ、TLX和LD种群之间均没有形成天然的地理阻隔，南盘江和红水河两岸的种群基因交流频繁。此外，本文所研究的黑颈长尾雉4个地理种群之间没有遗传分化，因此，建议把这4个地理种群当做一个管理单元进行保护管理。我们从MHCIIB exon 2外显子探讨其遗传多样性水平。我们从73个个体中发现了24个显著的等位基因。在4个种群中有7个共享的等位基因和6个稀有基因。大部分的个体含有1-5个等位基因，表明了黑颈长尾雉含有3个位点。dN ⁄ dS率（dN：非同义突变；dS：同义突变）大于1，表明MHCIIB exon 2受到了平衡选择。另外，我们检测到1-3个重组事件和75转换事件，重组和转换事件也增加了MHCIIB exon 2的多样性水平。系统演化树和网络分析显示黑颈长尾雉的等位基因并没有能聚类在一起，暗示了MHCIIB exon 2跨物种进化。