横断山区复杂地形与气候对川西白腹鼠种群地理分化的影响

Complex Terrain and Climatic Oscillations in Hengduan Mountains Influence Geographical Division of the Large White-bellied Rat(Niviventer excelsior)

横断山区地质地貌复杂,历史上经历了剧烈的抬升和循环的冰期,这些地质和气候变化对物种的分化产生了重要的影响。川西白腹鼠Niviventer excelsior是广泛分布于横断山区的鼠类物种。本研究基于线粒体cytb基因探讨来自四川、云南和西藏三地川西白腹鼠的种群分化。利用最大简约法(Maximum Parsimony)、最大似然法(Max-imum Likelihood)和贝叶斯推断(Bayesian Inference)构建系统发育树。系统发育树显示川西白腹鼠和安氏白腹鼠Niviventer andersoni没有形成交互单系,二者可能有不完全谱系分拣或基因渐渗现象。川西白腹鼠种群存在亲缘地理结构,大体按理塘-稻城一线分为两个进化支Clade A和Clade B。sub-clade A1来自川西地区(包括九龙、康定、丹巴和二郎山)和云南泸水;sub-clade A2来自滇西地区的哀牢山。在Clade B中,sub-clade B1全都是来自西藏察瓦龙;sub-clade B2则来自川西北地区,包括炉霍卡沙湖、雅江和巴塘。支持滇西亚种N.e.tengchongnsis和指名亚种N.e.excelsior的分化。川西白腹鼠的种群分化可能与横断山区地形的复杂性和在历史上该地区多次的抬升和气候的波动有关。

The Hengduan Mountains have undergone dramatic geological and climatic changes over the Pleistocene. The population structures of animals in this region have been significantly influenced by geographic changes and repeated glacial events during the Pleistocene,especially the last glaciations. The large white-bellied rat （Niviventer excelsior） is a rodent endemic to the Hengduan Mountains. In this study,twenty-three individuals collected from Sichuan,Tibet and Yunnan were used to investigate their genetic differentiation and evolutionary processes. The phylogenetic relationships were inferred by using maximum parsimony,maximum likelihood and Bayesian inference. The results assumed N. excelsior and N. andersoni were not monophyletic mutually,which were consequence of an incomplete lineage sorting or introgression. The topology indicated that N. excelsior has phylogeographical structure,which has correlation with their geographical origins. N. excelsior populations were isolated by Litang-Daocheng and clustered two major clades：Clade A and Clade B. In the Clade A,individuals from west Sichuan and Lushui,Yunnan clustered into sub-Clade A1; individuals from the Ailao Mountains,Yunnan clustered into sub-Clade A2. In the Clade B,sub-Clade B1 contained individuals from Chawalong,Tibet; sub-Clade B2 contained individuals from northwest Sichuan. Phylogenetic trees also supported subspecies N. e. tengchongensis and N. e. excelsior. These results indicated that complex topographic configuration in the Hengduan Mountains and climatic oscillations in Pleistocene promote genetic divergence of N. excelsior.