Li MinJie, Xie DengFeng, Xie Chuan, Deng YiQi, Zhong Yan, Yu Yan, He XingJin
Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China.
Front Plant Sci. 2019 Mar 5;10:149. doi: 10.3389/fpls.2019.00149. eCollection 2019.
The Qinghai-Tibet Plateau (QTP) has been biogeographically divided into the eastern monsoonal and the western continental climatic zones along the 500 mm isohyet. However, this biogeographic hypothesis has been rarely tested using a phylogeographic approach. The members of the genus subgenus coincidentally distribute across this biogeographical divide. Intriguingly, of subgenus co-occurs in the distribution range of subgenus . To illuminate the role of this biogeographic divide on the genetic divergence, we genotyped 466 individuals of 52 populations of subgenus and 110 individuals of 19 populations of using three chloroplast DNA fragments, whole nrITS and nine nuclear microsatellite loci, supplemented with the present environmental space and paleo-distribution modeling. Our phylogeographical evidence recovered the concordant east-west genetic breaks both for subgenus and . along the 500 mm isohyet. The divergence time estimations and environmental niche differentiations suggested this east-west genetic breaks could have been triggered by the climatic-induced vicariance during the early Pleistocene. Noticeably, this split within subgenus could have been deepened by the morphological vicariance from the eastern umbel to the western spicate, while that within could have been obscured due to the pollen flows from the east to west caused by the postglacial expansion. The genetic structures and ecological niche modelings (ENMs) recovered the distinct responses to the Quaternary climatic oscillations for species constricted to different climatic zones, further highlighting the profound effect of the climatic differences and tectonic uplifts on the genetic diversification. Overall, our findings offer strong evidence for the existence of a biogeographic divide between the eastern monsoonal and the west continental climatic zones of the QTP nearly along the 500 mm isohyet.
青藏高原（QTP）在生物地理学上沿着500毫米等雨量线被划分为东部季风气候区和西部大陆气候区。然而，这一生物地理学假说很少通过系统发育地理学方法进行检验。该属亚属的成员恰好分布在这条生物地理分界线两侧。有趣的是，亚属的成员与亚属的成员在分布范围内共存。为了阐明这条生物地理分界线对遗传分化的作用，我们对亚属52个种群的466个个体以及19个种群的110个个体进行了基因分型，使用了三个叶绿体DNA片段、完整的nrITS和九个核微卫星位点，并辅以当前环境空间和古分布模型。我们的系统发育地理学证据在亚属和亚属中都发现了沿着500毫米等雨量线一致的东西向遗传间断。分歧时间估计和环境生态位分化表明，这种东西向遗传间断可能是由早更新世期间气候引起的地理隔离所触发。值得注意的是，亚属内的这种分化可能因从东部伞形花序到西部穗状花序的形态地理隔离而加深，而亚属内的分化可能由于冰期后扩张导致的花粉从东向西流动而被掩盖。遗传结构和生态位模型（ENMs）揭示了局限于不同气候区的物种对第四纪气候振荡的不同响应，进一步突出了气候差异和构造隆升对遗传多样化的深远影响。总体而言，我们的研究结果为青藏高原东部季风气候区和西部大陆气候区之间几乎沿着500毫米等雨量线存在生物地理分界线提供了有力证据。
