Phylogeography and genetic diversity of East Asian Neolitsea sericea (Lauraceae) using chloroplast DNA sequence variation

초록

Neolitsea sericea (Lauraceae) is an evergreen broad-leaved tree growing in East Asian warm-temperate regions. The species is a common plant of evergreen forests in Korea and Japan, and shows a disjunctive distribution on the Lanyu Island, Taiwan and the archipelago Zhoushan, China. We attempt to reconstruct the phylogeographic history of this species and to infer the refugia of warm-temperate evergreen broad-leaved plants in the Far East during the Quaternary ice age. We identified the chloroplast DNA haplotypes of 325 individuals from 36 populations covering entire geographic range of the species based on sequence data from trnL-F and psbC-trnS intergenic spacers and rps16 intron. The nine haplotypes were identified and the haplotype network constructed using the program TCS. To examine the genetic structure an analysis of molecular variance (AMOVA) was also carried out. No dominant haplotype was widespread over the entire distributional range of this species. Most of the haplotypes were revealed in Chukoku region of Japan, so that the region is supposed to be the refugia during the climatic oscillations. Rare haplotypes are found in Korea and Lanyu Island respectively. Two haplotypes detected in archipelago Zhoushan are common to the populations of Korea and Japan. Our results indicated that the present haplotype distribution of the species has resulted from multiple migrations through land bridges connecting Japan to the Asian continent or Taiwan during the glacial periods and the isolations of populations have occurred according to sea level rising after the ice age.