Format: ORAL

LiGuo Zhang1, XiaoQian Li2, WeiTao Jin1, YuJuan Liu1, Yao Zhao1, Jun Rong1, XiaoGuo Xiang1,*

1 School of Life Sciences, Nanchang University, Nanchang, China 2 Institute of Botany, Chinese Academy of Sciences, Beijing, China

The tropical Asian and Australasian floras have a close relationship, and is a vital distribution pattern of seed plants worldwide. As estimated, more than 81 families and 225 genera of seed plants distributed between tropical Asia and Australasia. However, the evolutionary dynamics of two floras were still vague. Here, a total of 29 plant lineages, represented the main clades of seed plants and different habits, were selected to investigate the biotic interchange between tropical Asia and Australasia by integrated dated phylogenies, biogeography, and ancestral state reconstructions. Our statistics indicated that 68 migrations have occurred between tropical Asia and Australasia since the middle Eocene except terminal migrations, and the migration events from tropical Asia to Australasia is more than 2 times of the reverse. Only 12 migrations occurred before 15 Ma, whereas the remaining 56 migrations occurred after 15 Ma. The MDE (maximal number of potential dispersal events) analysis also show obviously asymmetry with southward migration as the main feature, and indicated the climax of two direction migrations occurred after 15 Ma. We speculated that the formation of island chains after the AustralianSundaland collision and climate changes have been beneficial for seed plants migrations since the midMiocene. Furthermore, biotical dispersal and stable habitat may be crucial for floristic interchange among tropical Asia and Australasia. Thus, this study provides evidence for the past floristic exchanges between tropical Asia and Australasia.