Phylogeography and genetic diversity of East Asian Neolitsea sericea (Lauraceae) based on variations in chloroplast DNA sequences.

Neolitsea sericea is an evergreen broad leaved tree in the warm-temperate regions of East Asia. This area is a hotspot for plant species richness and endemism caused by dynamic changes in land configuration during the Quaternary. However, the historical migration of such evergreen tree species is still poorly understood. In an attempt to reconstruct the phylogeographic history of N. sericea during the Quaternary, we identified the chloroplast DNA haplotypes of 287 individuals from 33 populations covering almost all of its geographic range. Analyses were based on sequence data from the trnL-F, psbC-trnS, and rps16 regions. Nine haplotypes were identified. The majority included ancestral types in the southwestern part of the main islands of Japan, with other region-specific haplotypes being found in populations on the Korean Peninsula, Taiwan (Isl. Lanyu), and elsewhere in Japan. A statistical parsimony network revealed two lineages derived from Japanese main islands. One was represented on the Korean Peninsula, the other on Isl. Lanyu. The current distribution of N. sericea has been shaped by colonization via land bridges. During the glacial periods, two primary, but separate migration routes were followed--from the southwestern part of the Japanese main islands to either the Korean Peninsula or Taiwan. In addition, we believe the Zhoushan populations were shaped by post-glacial processes through an ECS land bridge (East China Sea basin) from northern refugia that existed during the late Pleistocene.