中国-日本植物区系中的谱系地理间断及其形成机制

Phylogeographic breaks and the mechanisms of their formation in the Sino-Japanese floristic region

中国-日本植物区系极高的物种多样性是由多样的地形和气候条件、复杂的地质气候历史和海平面变化共同作用形成的。在揭示物种多样性形成和分化的驱动力时,谱系地理学是一个有效的手段。以往的谱系地理研究表明谱系地理间断,即不同基因谱系间的间断普遍存在。由西向东,7个普遍存在的谱系地理间断位置位于湄公河-怒江分水岭、田中-楷永线、四川盆地、105°E附近、第二三阶梯分界线、华北地区以及东海和朝鲜海峡。这些谱系地理间断的形成可归因于历史因素和生态因素,往往由地理隔离和环境隔离共同起作用。历史因素是地质事件和气候变化,主要包括青藏高原隆起,亚洲季风和内陆干旱的形成与增强,干旱带的重新增强以及第四纪的气候波动和海平面变化。生态因素是适应性分化,即不同环境中不同选择压力下形成的分化,适应性分化可阻碍不同种群间的基因流,形成谱系地理间断。不过,同一谱系地理间断并不是在所有植物中共享,因为不同植物有不同的生物学特性,主要是扩散能力不同。最后,该文从分化时间的准确估计、地理隔离和环境隔离的相对贡献率以及比较谱系地理学的应用3个方面对未来谱系地理间断研究的发展趋势进行了展望。

Due to combinations of diverse geography and climate,and complex geo-climate histories and sea level fluctuations,the Sino-Japanese floristic region has extremely high species diversity.Phylogeography is an effective method to identify the factors triggering the formation and differentiation of species diversity.Previous studies showed that phylogeographic breaks,the genetic discontinuity between different gene genealogies,were ubiquitously present.From the west to the east,seven general phylogeographic breaks occur,including the MekongSalween Divide,the Tanaka-Kaiyong Line,the Sichuan Basin,ca.105° E,the boundary between the Second and Third ladders,the North China,and the East China Sea and Korea Strait.These phylogeographic breaks are mainly attributable to both historical and ecological factors,which are generally due to a combined effect of the isolation by distance（IBD） and the isolation by environment（IBE）.Geological events and climate changes are the historical factors,mainly including the uplift of Qinghai-Xizang Plateau,the formation and intensification of the Asian monsoon and the Asian interior aridification,the redevelopment of the arid belt,and the Quaternary climate oscillations and sea level fluctuations.Adaptive divergence,namely the divergence induced by different selective pressures under different environments,is responsible for the ecological factors.Adaptive divergence could obstacle gene flow among populations,resulting in the formation of phylogeographic break.However,an identical phylogeographic break is not shared by all the plants because of their various intrinsic biological characteristics,among which the difference in dispersal ability is most important.Finally,we envisaged the future development of phylogeographic break studies based on accurate divergence time estimation,relative contribution of IBD and IBE,and also the utilization of comparative phylogeography.