Origin and evolution of the flora and fauna of Hainan Island, China

This review was made by Zhu Hua from Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. Phylogenetic and molecular biogeographic studies of the biological taxa involving Hainan Island showed that the genera and species appeared and diverged early in their evolution can be explained by the land connection between Hainan Island, Vietnam, and Guangxi before the Middle Miocene; while for the later divergent taxa after the Middle Miocene, such as population divergence of species (usually only a few million years), their patterns can be explained by Hainan Island and Leizhou Peninsula having been close or connected by land. This is exactly in line with the idea that Hainan Island connected southwest Guangxi and northern Vietnam before the Miocene and later moved to its present position proposed by geological tectonics.

Palaeobotanical data showed that in the Eocene, Hainan Island had subtropical vegetation and flora similar to the ones in southwest Guangxi, suggesting that in the Paleogene, Hainan Island may have been located near or on the southwest border of Guangxi and northern Vietnam, rather than in its present location. The flora and vegetation of Hainan Island could have evolved from subtropical to tropical, implying that Hainan Island has moved southeast since the Oligocene. 

Research on the flora of Hainan Island showed that its current floristic division basically displays a northeast-southwest inclined distribution pattern, which supports the results of paleomagnetic studies that Hainan Island witnessed anti-clockwise rotation during its southeast movement.

It was concluded that the Middle Miocene (15–10 Myr) could be a time node.  Prior to this period, the retrieved literature on phylogenetic patterns at genus and species levels showed that Hainan Island had a close relationship with northern Vietnam and southwest Guangxi. After the Middle Miocene, the genetic differentiation of the population in species was influenced by land bridge connections between Hainan Island and China mainland, but this did not affect all species.