Shahzad Khurram, Jia Yun, Chen Fu-Lin, Zeb Umar, Li Zhong-Hu
Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China.
Front Plant Sci. 2017 Nov 8;8:1929. doi: 10.3389/fpls.2017.01929. eCollection 2017.
Mountain uplift and climatic fluctuations are important driving forces that have affected the geographic distribution and population dynamics history of organisms. However, it is unclear how geological and climatic events might have affected the phylogeographic history and species divergence in high-alpine herbal plants. In this study, we analyzed the population demographic history and species differentiation of four endangered herbs on the high-altitude Qinghai-Tibetan Plateau (QTP) and adjacent areas. We combined phylogeographic analysis with species distribution modeling to detect the genetic variations in four species (, , , and ). In total, 559 individuals from 74 populations of the four species were analyzed based on three maternally inherited chloroplast fragments (, , and SG) and one nuclear DNA region (internal transcribed spacer, ITS). Fifty-five chloroplast DNA (cpDNA) and 48 ITS haplotypes were identified in the four species. All of the cpDNA and ITS haplotypes were species-specific, except and shared one cpDNA haplotype, H32. Phylogenetic analysis suggested that all four species formed a monophyletic clade with high bootstrap support, where and were sisters. In addition, each species generated an individual clade that corresponded to their respective species in the ITS tree. Population dynamics analyses and species distribution modeling showed that the two widely distributed herbs and exhibited obvious demographic expansions during the Pleistocene ice ages. Molecular dating suggested that the divergence of the four species occurred approximately between 3.6 and 1.2 Mya, and it was significantly associated with recent extensive uplifts of the QTP. Our results support the hypothesis that mountain uplift and Quaternary climatic oscillations profoundly shaped the population genetic divergence and demographic dynamics of species. The findings of this and previous studies provide important insights into the effects of QTP uplifts and climatic changes on phylogeography and species differentiation in high altitude mountainous areas. Our results may also facilitate the conservation of endangered herbaceous medicinal plants in the genus
山脉隆升和气候波动是影响生物地理分布和种群动态历史的重要驱动力。然而，地质和气候事件如何影响高山草本植物的系统地理学历史和物种分化尚不清楚。在本研究中，我们分析了青藏高原及邻近地区四种濒危草本植物的种群历史和物种分化。我们将系统地理学分析与物种分布建模相结合，以检测四种植物（、、和）的遗传变异。基于三个母系遗传的叶绿体片段（、和SG）和一个核DNA区域（内转录间隔区，ITS），总共分析了来自这四个物种74个种群的559个个体。在这四个物种中鉴定出了55个叶绿体DNA（cpDNA）单倍型和48个ITS单倍型。除和共享一个cpDNA单倍型H32外，所有cpDNA和ITS单倍型均为物种特异性。系统发育分析表明，所有四个物种形成了一个具有高自展支持率的单系类群，其中和是姐妹种。此外，每个物种在ITS树中都产生了一个与其各自物种相对应的单独类群。种群动态分析和物种分布建模表明，两种广泛分布的草本植物和在更新世冰期表现出明显的种群扩张。分子定年表明，这四个物种的分化大约发生在360万至120万年前，并且与青藏高原近期的大规模隆升显著相关。我们的结果支持了这样的假设，即山脉隆升和第四纪气候振荡深刻地塑造了这些物种的种群遗传分化和种群动态。本研究及先前研究的结果为青藏高原隆升和气候变化对高海拔山区系统地理学和物种分化的影响提供了重要见解。我们的结果也可能有助于保护该属濒危草本药用植物。
