Format: ORAL

Pei-Han Huang1,2,6, Tian-Rui Wang2,3,6, Min Li1,6, Zi-Jia Lu2,5, Ren-Ping Su1,6, Ou-Yan Fang1,6, Lang Li1, Shi-Shun Zhou4, Yun-Hong Tan4, Hong-Hu Meng1,4, Yi-Gang Song2, Jie Li1

1 Plant Phylogenetics and Conservation Group, Center for Integrative Conservation & Yunnan Key Laboratory for Conservation of Tropical Rainforests and Asian Elephants, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China 2 Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China 3 Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China 4 Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Nay Pyi Taw 05282, Myanmar 5 College of Life Sciences, Shanghai Normal University, 100 Guilin Rd., Shanghai 200234, China 6 University of Chinese Academy of Sciences, Beijing 100049, China

Demonstrating whether the plate-tectonic drifts of Hainan Island occurred and affected the evolutionary of plants will disentangle the issue puzzled natural scientists over decades. Here, Engelhardia roxburghiana around Hainan Island was selected to identify the genetic structure, diversity, and demographic dynamics using RAD-seq. Three lineages were identified and the divergence time and genetic structure showed that E. roxburghiana dispersed from Chiang-nan to Hainan Island via land bridge during the late Eocene. Hence, drift of Hainan Island did not occur, which was impossible to affect the evolutionary trajectory of plants. Higher genetic diversity in Yunnan-Guizhou Plateau and Chiang-nan Hilly Ranges are the results of mixed populations or refugia, while lower genetic diversity in the Indochina Peninsula due to historical bottleneck. During the late Eocene to Oligocene, the north shift of arid belt driven E. roxburghiana expand from Indochina Peninsula to southern China, and main diversification occurred in Miocene within the monsoon system. The climatic oscillations during Quaternary led to the expansion but there was slight contraction after LGM, while southern China was and will be the refugia to climate change. This is the first comprehensive work from large-scale SNP features, providing genomic insights into the geological history of Hainan Island from biogeographic patterns of E. roxburghiana,itsheds light on geological history of Hainan Island and illuminates the biogeographic patterns of island-mainland in the regions.