Xiao Jian-Hua, Ding Xin, Li Lang, Ma Hui, Ci Xiu-Qin, van der Merwe Marlien, Conran John G, Li Jie
Plant Phylogenetics and Conservation Group Centre for Integrative Conservation Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences Kunming China.
University of Chinese Academy of Sciences Beijing China.
Ecol Evol. 2020 Aug 26;10(19):10543-10557. doi: 10.1002/ece3.6710. eCollection 2020 Oct.
Understanding the role of climate changes and geography as drivers of population divergence and speciation is a long-standing goal of evolutionary biology and can inform conservation. In this study, we used restriction site-associated DNA sequencing (RAD-seq) to evaluate genetic diversity, population structure, and infer demographic history of the endangered tree, which is distributed around the Sichuan Basin. Genomic patterns revealed two distinct clusters, each largely confined to the West and East. Despite sympatry of the two genomic clusters at some sites, individuals show little or no evidence of genomic introgression. Demographic modeling supported an initial divergence time between the West and East lineages at ~15.08 Ma with further diversification within the West lineage at ~7.12 Ma. These times largely coincide with the two independent intensifications of the East Asian monsoon that were initiated during the middle (Langhian) and late Miocene (Messinian), respectively. These results suggest that the Miocene intensification phases of the East Asian monsoon played a pivotal role in shaping the current landscape-level patterns of genetic diversity within , as has been found for the interspecific divergence of other subtropical Chinese plants. Based on isolation-by-distance and species distribution modeling, we hypothesize that followed a ring diversification which was facilitated by the Sichuan Basin acting as barrier to gene flow. In situ and ex situ conservation management plans should consider the results obtained in this study to help secure the future of this beautiful and culturally significant endangered tree.
了解气候变化和地理因素作为种群分化和物种形成驱动因素的作用，是进化生物学的一个长期目标，并且可为保护工作提供参考。在本研究中，我们使用限制性位点关联DNA测序（RAD-seq）来评估一种分布于四川盆地周边的濒危树木的遗传多样性、种群结构，并推断其种群历史。基因组模式揭示了两个不同的聚类，每个聚类在很大程度上局限于西部和东部。尽管在某些地点两个基因组聚类同域分布，但个体几乎没有或完全没有基因组渐渗的证据。种群动态建模支持西部和东部谱系之间的初始分化时间约为1508万年前，西部谱系内部在约712万年前进一步分化。这些时间大致与东亚季风分别在中新世中期（郎山期）和晚期（墨西拿期）开始的两次独立增强期相吻合。这些结果表明，东亚季风的中新世增强阶段在塑造该树种当前景观水平的遗传多样性模式中起了关键作用，正如在其他中国亚热带植物的种间分化中所发现的那样。基于距离隔离和物种分布建模，我们推测该树种遵循了环状多样化模式，四川盆地作为基因流动的障碍促进了这种模式。原地和迁地保护管理计划应考虑本研究获得的结果，以帮助确保这种美丽且具有文化意义的濒危树木的未来。
