EAPSI: Investigating Historical Changes in Montane River Systems and Their Roles in Species Diversification

古老的地质事件，如河流流域的变化和山脉的形成，可以对生物的遗传结构和进化产生深远的影响。通过分析不同生物种群在复杂环境中的遗传多样性，可以推断这种历史过程的时间和分布及其对物种进化的影响。横断山区位于青藏高原与中国西南低地的过渡地带。该地区的独特之处在于拥有重复的、平行的、山地河流系统，这些河流系统横跨显著的海拔和环境梯度。研究表明，由于欧亚大陆与印度的大陆碰撞以及随后青藏高原的形成，该地区的主要河流(湄公河、萨尔温江和长江)过去的排水方式和流向发生了重大变化，这些地质事件影响了该地区一些水生动植物的遗传结构。然而，河流地形变化的时间和地理范围仍然知之甚少，到目前为止，关于这种事件对陆地脊椎动物进化的影响尚不清楚。日本蜥蜴属的蜥蜴物种被认为与HMR的河流系统的栖息地密切相关。由于HMR特有的许多物种，陆地蜥蜴群非常适合研究历史地质和环境变化对该地区种群和物种多样性的影响。这项研究将与中国科学院的车博士合作，利用现代分子技术对HMR特有蜥蜴的基因数据进行研究。通过对青藏高原地区蜥蜴物种多样性的野外调查和重点种群遗传多样性的实验室研究，这项研究不仅将促进脆弱生态系统中重点种群的生物多样性和保护研究，而且将进一步加深我们对青藏高原形成对河流水系变化和脊椎动物多样性的历史重要性的认识。在中国横断山区(横断山区和扬子江)，增加对日本蜥蜴属局部蜥蜴物种的现有分类和地理样本。结合中国主办机构已有的样本，将从组织样本中提取基因组DNA，并在中国主办机构进行靶基因(线粒体和核)的扩增和测序。系统发育学方法将被用来研究种群遗传和生物地理模式，并估计HMR地区局部蜥蜴物种之间的谱系分化时间。研究结果将被用来建立生物地理学假说，即河流系统的历史变化和山脉的形成在青藏高原周围的脊椎动物多样性中所起的作用。该奖项由东亚和太平洋夏季研究所项目设立，支持一名美国研究生的夏季研究，由NSF和中国科技部联合资助。

Ancient geological events such as changes in river drainages and the formation of mountain ranges can have profound impacts on the genetic structure and evolution of organisms. By analyzing the genetic diversity of different populations of organisms across complex environments, inferences can be made about the timing and distribution of such historical processes and their impacts on species evolution. The Hengduan Mountain Region (HMR) is positioned at the transition zone between the Tibetan Plateau and lowland southwest China. This region is unique in having repeated, parallel, montane river systems that run across dramatic elevational and environmental gradients. Studies have shown that the major rivers of the region (Mekong, Salween, and Yangtze) have experienced significant changes in drainage patterns and flow directions in the past due to the continental collisions between Eurasia and India and the subsequent formation of the Tibetan Plateau, and these geological events have impacted genetic structures among some aquatic animals and plants in the region. However, the timing and geographic scope of changes in river topology remain poorly understood, and nothing is known to date about the impact of such events on the evolution of terrestrial vertebrates. Lizard species of the genus Japalura are recognized to be associated closely with habitats along river systems in the HMR. With many species endemic to the HMR, the group of terrestrial lizards is well suited for investigating the impact of historical geologic- and environmental-changes on population and species diversification in the region. In collaboration with Dr. Jing Che from the Chinese Academy of Sciences, this research will employ modern molecular techniques to the genetic data of endemic lizards in the HMR. Through field-based surveys of species diversity of lizards and lab-based studies of genetic diversity of the focal species group across the HMR, this research not only will promote biodiversity and conservation studies of the focal species group in a fragile ecosystem, but also, it will further our knowledge of the historical importance of the formation of the Tibetan Plateau for changes in river systems as well as for vertebrate diversification in the HMR.During the research period in China, fieldwork will be conducted in targeted valley habitats along the three major rivers (Mekong, Salween, and Yangtze) in the Hengduan Mountain Region (HMR) of China to increase available taxonomic and geographic sampling of focal lizard species in the genus Japalura. Combined with samples available already at the host institution in China, genomic DNA will be extracted from tissue samples, and target genes (mitochondrial and nuclear) will be amplified and sequenced at the host institute in China. Phylogenetic approaches will be employed to study population genetic and biogeographic patterns, and estimate the timing of lineage divergence, among focal lizard species across the HMR. The results will be used to formulate biogeographical hypotheses concerning the role that historical changes in river system and formation of mountain ranges played in the vertebrate diversification around the Tibetan Plateau.The award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Chinese Ministry of Science and Technology.