近日,国际著名杂志PLoS One在线刊登了中科院昆明动物研究所研究人员的最新研究成果“Phylogeographic Study of Apodemus ilex (Rodentia: Muridae) in Southwest China,”,文章中,作者在哺乳动物分子系统地理学研究获得新进展。
喜马拉雅-横断山地区是世界性的生物多样性热点地区之一,也是中国西南山地生物多样性热点地区生物多样性保护优先区。该区域有着地球上最复杂水系、山系和复杂的地质历史,其独特的自然地理条件使该区域成为中国乃至世界各种自然资源最富集的地区之一,同时又保存着若干本区特有的生物类群,使其成为若干生物演化的中心,形成了自身的生物多样性特色,构成了一座生物资源丰富的物种基因库。青藏高原地形的改变和横断山脉的走向被广泛认为是影响我国西南地区物种空间分布和遗传多样性因素的重要因素。因此,喜马拉雅-横断山地区不仅是动物孓遗的重要避难中心,还是研究生物地理学很好的模式系统。但是,迄今,关于该区域地质历史事件和气候变迁如何影响生物遗传多样的研究却少有报道。
昆明动物研究所遗传资源与进化国家重点实验室兽类生态与进化组的刘琦等同学在导师蒋学龙研究员指导下,以鼠科中最古老的属之一—姬鼠属(Apodemus)为研究对象,在喜马拉雅-横断山地区广泛采集姬鼠标本并收集相关采集地和标本生态信息,在查对姬鼠属种类的化石标本及其记录的基础上,以喜马拉雅-横断山地区特有的澜沧江姬鼠(Apodemus ilex)为生物地理学研究模型,展开姬鼠属的起源与演化和生物地理学研究。基于中华姬鼠(A. draco)和澜沧江姬鼠(A. ilex)的分类地位仍然广存争议,研究针对采集自喜马拉雅-横断山地区51个采集点共计203个中华姬鼠复合种群(A. draco complex)样品结合姬鼠属其他11个种进行了分子系统发育研究、松散分子钟估算和生物地理分析。研究结果显示,澜沧江姬鼠(Apodemus ilex)和中华姬鼠(A. draco)是位于姬鼠属的分支末端的两个姐妹种;澜沧江姬鼠(Apodemus ilex)的独立地位得到验证,大约在上新世末期2.25个白万年前与中华姬鼠(A. draco)独立分化开;澜沧江姬鼠(Apodemus ilex)在更新世中期的玉龙冰期以澜沧江为界分化为东西两个大的支系;在更新世中晚期,澜沧江以西的种群又在丽江冰期以怒江为界分化为两个亚支系,澜沧江以东的种群也在同期分化为两个亚支系;在冰期前后,各种群存在以河谷为阻限的南北多次扩散。研究结果表明,喜马拉雅-横断山地区复杂的地质地貌,尤其是水流湍急地纵谷对种群的隔离是造成这种小型啮齿类分化的主要原因,同时,古气候的变化是驱动该物种各亚支系的分化和扩散的重要因素;该结果也从分子生物地理学的角度暗示了喜马拉雅-横断山地区部分水系的形成先后假说以及河流袭夺假说,提示我们继续利用比较生物地理学研究方法探讨该复杂区域的地质历史、气候变迁对生物多样性的影响。(生物谷Bioon.com)
doi:10.1371/journal.pone.0031453
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Phylogeographic Study of Apodemus ilex (Rodentia: Muridae) in Southwest China
Qi Liu1,2#, Peng Chen1,2#, Kai He1,2#, C. William Kilpatrick3, Shao-Ying Liu4, Fa-Hong Yu5*, Xue-Long Jiang1*
Background The Mountains of southwest China have complex river systems and a profoundly complex topography and are among the most important biodiversity hotspots in the world. However, only a few studies have shed light on how the mountains and river valleys promote genetic diversity. Apodemus ilex is a fine model for investigating this subject. Methodology/Principal Findings To assess the genetic diversity and biogeographic patterns of Apodemus ilex, the complete cytochrome b gene sequences (1,140 bp) were determined from 203 samples of A. draco/ilex that were collected from southwest China. The results obtained suggested that A. ilex and A. draco are sistergroups and diverged from each other approximately 2.25 million years ago. A. ilex could be divided into Eastern and Western phylogroups, each containing two sub-groups and being widespread in different geographical regions of the southern Hengduan Mountains and the western Yunnan - Guizhou Plateau. The population expansions of A. ilex were roughly from 0.089 Mya to 0.023 Mya. Conclusions Our result suggested that A. ilex is a valid species rather than synonym of A. draco. As a middle-high elevation inhabitant, the phylogenetic pattern of A. ilex was strongly related to the complex geographical structures in southwest China, particularly the existence of deep river valley systems, such as the Mekong and Salween rivers. Also, it appears that the evolutionary history of A. ilex, such as lineage divergences and population expansions were strongly affected by climate fluctuation in the Late Pleistocene.