商城肥鲵的扩散与谱系地理学研究

Pachyhynobius shangchengensis is an endangered stream salamander, endemic to Dabie Mountain. For deforestation, habitat loss and illegal catch, Shangcheng stout salamander underwent lasting population decline. In order to obtain more details of the species and do a better conservation work, a molecular ecology research project was put forward on the dispersal and phylogeogarphy of P. shangchengensis. .(i) Sex-biased dispersal pattern. The local resource competition hypothesis and the local mate competition hypothesis were developed based on avian and mammalian systems to explain sex-biased dispersal. Most avian species show a female bias in dispersal, due to resource defence, and most mammals show a male bias for male-male competition. Little is known about sex-biased dispersal in amphibian. Resource defence and male-male competition are both intense in P. shangchengensis, the stream salamander, so we'll test whether sex-biased dispersal in P. shangchengensis is consistent with the local resource competition hypothesis (female-biased) or the local mate competition hypothesis (male-biased). Using nuclear DNA mircosatellite as molecular marker, combined with fine-scale genetic spatial autocorrelation analyses, we'll find the potential sex-biased dispersal pattern. .(ii) Dispersal approach. Whether P. shangchengensis spread strictly by stream pathways? Or it has potential dispersal approach by overland pathways? By applying a consistent sampling design that encompassed three hierarchical scales (streams, catchments, basins) and multi microsatellite loci, we'll investigate the genetic structure of P. shangchengensis populations in river networks, and then test different models of population structure by estimating the correlation between Fst and correspending distance model. Based on above analysis, we should summarize the potential dispersal approach of P. shangchengensis through the stream networks. .(iii) Phylogeography study. Climatic changes associated with Pleistocene glacial cycles profoundly affected species distributions, patterns of gene flow, and demography. Pachyhynobius shangchengensis was restricted to high-elevation streams on montane habitats, ranges may expand and contract along an elevational gradients in response to environmental fluctuations. We use DNA sequence data (ND2, ND4, Cytb) along with ecological niche modelling and coalescent simulations to test several hypotheses of phylogeographic pattern of P. shangchengensis. Then the effect of Pleistocene climatic fluctuations was assessed, especially on evolutionary lineage diversification and historical demography of P. shangchengensis. .Above research contents will provide more valuable information for the conservation work of P. shangchengensis.

商城肥鲵是大别山地区特有的两栖动物，由于森林砍伐及栖息地退化等因素，导致其种群持续下降。为了深化对该物种的了解以做好保护工作，本项目通过分子生态学途径就商城肥鲵的扩散和谱系地理学进行研究：（1）使用微卫星为遗传标记，通过遗传空间自相关分析等检验来探讨自然环境下商城肥鲵性别偏倚的扩散模式。（2）通过分析遗传变异在溪流网络不同等级尺度（溪流、集水区、流域）中的分布格局，并结合对遗传结构不同模型的检验，了解商城肥鲵在溪流网络中的扩散途径。（3）使用线粒体DNA多基因序列（ND2、ND4、Cytb）作为遗传标记进行谱系分析，同时采用生态位模型、GIS 技术、古气候环境模拟等技术手段对其分布区的变化进行分析，进而重现谱系地理格局的形成过程，探讨更新世气候波动对低纬度山区敏感物种的谱系分化和有效种群变化的影响。通过上述研究以期对商城肥鲵有更全面的认识，并为保护管理工作提供更为详备的研究基础和理论支持。

商城肥鲵是大别山地区特有的小鲵类，目前自北向南分布有6个种群：金刚台（JTX）、康王寨-黄柏山-九峰尖（KHJ）、马鬃岭（MW）、天堂寨（TTZ）、白马尖-鹞落坪-明堂山（BYM）、枯井园种群（KJY）。本项目以分子生态学途径就下列进行了研究。在谱系地理学研究中，商城肥鲵各种群都显示出较高的遗传多样性。在商城肥鲵群体中存在很明显的三个遗传聚类，分别对应北部（JTX, KHJ）、中部（MW, TTZ）、南部（BYM、KJY）。各种群形成五个明显的谱系（JTX, KHJ, MW, TTZ, BYM-KJY），各谱系分歧时间在451万-169万年前。其种群保持了长期稳定，受冰期干冷气候影响在50万年出现下降，而在在末次间冰期（MIS5）又出现显著的种群增长，总体来看，种群历史动态与冰期循环相契合。通过生态位建模结果，商城肥鲵的分布区从末次盛冰期（2.2万年前）以来至2050年都无明显变化，主成分分析则显示各种群间生态位已经出现分化。分布区特征说明空岛效应导致商城肥鲵在大别山区形成谱系的深度分歧和生态位的分化。在偏性扩散研究中发现商城肥鲵为偏雄扩散，其雄、雌的校正分配系数分别为 -0.005 （0.179）和 0.006（0.219）。这提示商城肥鲵群体中可能存在着强烈的配偶资源竞争。空间自相关分析显示，商城肥鲵在相对较小的空间尺度下（<430m）未显现出显著性的空间遗传格局，遗传格局与空间距离之间无明显的相关性而呈随机分布。这一结果提示了它们在河流中较强的扩散能力。同时，研究中也发现瀑布、地表地表径流缺失等景观特征对其遗传分化有明显影响。在扩散模式的研究中，空间自相关分析显示在2 km距离等级中出现显著的正自相关系数（r），说明个体的扩散行为一般多限于在2 km的空间范围内，多距离等级尺度空间自相关性分析则提示扩散尺度应不超过5-7 km。Barrier 分析表明，总体上江淮分水岭对商城肥鲵是一个显著的地理阻隔，但阻隔效果同时可能受到地形及景观因素的影响，为个体扩散提供可能。