古地质和古气候变迁是影响生物多样性和群体结构的两个重要因素。例如,影响北美洲和欧洲生物多样性的主要因素是第四纪冰期气候波动。然而中国南方孕育着复杂的地形,第四纪时并没有发育大规模的冰川,气候波动对于该地区生物的影响希待探究。另外,青藏高原的多次隆升造成中国西南地区地形和水系的巨大变动。其中,古长江流域的四川段原向西南流入南海,由于地形改变其逐渐流向东北方向,2-3个百万年时在三峡地区与长江中游水系连通,形成现代长江的雏形。古水系变迁对于生物的影响也是系统地理学近年来的研究热点。
分子进化与基因组多样性研究组博士生颜芳在张亚平院士和车静研究员的指导下,以中国南方特有两栖类棘腹蛙(Quasipaa boulengeri)为研究对象,使用线粒体和核基因为分子标记,发现棘腹蛙类群有四个分化较深的进化支系。
这四个支系的分化发生于较为古老的两个时期,大致对应于青藏高原的第二三次隆升时期,远早于第四纪冰期。而长江水系在三峡地区的连通介导了该物种从上游地区向中游地区的扩散,形成现今广泛的分布模式。虽然经历了第四纪的气候波动,但棘腹蛙种群基本保持稳定,没有经历过群体扩张或收缩等事件。这些结果证明地质变动是影响该群体演化的主要因素,而第四纪气候波动并没有对该物种产生显著作用。另外还发现四川盆地的东南地区是四个支系的二次接触地,并有基因流现象。
本研究揭示,在中国南方地区,第四纪冰期气候波动对山区两栖类的群体演化并没有显著的影响,而这可能是中国南方山区物种较为普遍的模式,对于今后的研究具有指导意义。该研究结果已发表于国际著名杂志Molecular Ecology。(生物谷Bioon.com)
DOI: 10.1111/mec.12153
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Geological events play a larger role than Pleistocene climatic fluctuations in driving the genetic structure of Quasipaa boulengeri (Anura: Dicroglossidae)
Fang Yan, Weiwei Zhou, Haitao Zhao, Zhiyong Yuan, Yunyu Wang, Ke Jiang, Jieqiong Jin, Robert W-Murphy, Jing Che, Yaping Zhang.
Paleoclimatic and paleogeological events have been identified as being the two main drivers of genetic structuring in extant organisms. We used a montane stream-dwelling frog, Quasipaa boulengeri, to explore the relative roles played by these drivers on species in southern China, a region needing thorough studies. We detected four major matrilines, and no broadly distributed haplotypes occurred. The complex orogenesis of south-western China drove matrilineal divergence in Q. boulengeri into highly structured geographical units. These matrilines subsequently persisted in situ with stable populations rather than undergoing expansions during glacial cycling. The unification of the upper and middle Yangtze River in the Three Gorges mountain region mediated downstream colonization of this frog. Analyses identified geological events as playing a larger role than climatic fluctuations in driving the population history of Q. boulengeri. Nuclear allele analyses indicated gene flow; this maintained genetic cohesion of the species. South-eastern Sichuan Basin was identified as the area of secondary contact for several matrilines, and this area deserves further study and special protection.