Tempo and Mode of Floristic Exchanges between Hainan Island and Mainland Asia: A Case Study of the Persea Group (Lauraceae)

The origin of island biodiversity has been a topic of interest in biogeography. Two main hypotheses were suggested to explain the floristic origin of Hainan Island: ancient vicariance vs. recent dispersal. The Persea group of Lauraceae was used to examine their origin on Hainan Island. A data matrix including five genera and 49 species was assembled, phylogenetic trees of the Persea group were reconstructed using both maximum likelihood and Bayesian inference methods, and a relaxed molecular clock in BEAST was used to estimate the divergence time of the Persea group. The results showed that the Persea group diverged from its sister clade in the Eocene, and that the endemic and common species of Hainan Island and mainland Asia originated relatively late during the Miocene–Pleistocene. Species of the Persea group on Hainan may have arrived from mainland Asia via dispersal or originated via dispersal–isolation–divergence during the Miocene and Pleistocene. The results favor the dispersal hypothesis for the origin of the flora of Hainan Island and negate the vicariance hypothesis.