title: Population demographic history of a temperate shrub,Rhododendron weyrichii(Ericaceae), on continental islands of Japan and South Korea.
abstract: Continental islands provide opportunities for testing the effects of isolation and migration on genetic variation in plant populations. In characteristic of continental islands is that the geographic connections between these islands, which are currently distinguished by seaways, have experienced fluctuations caused by sea-level changes due to climate oscillations during the Quaternary. Plant populations on the islands have migrated between these islands via the exposed seafloors or been isolated. Here, we examined the demographic history of a temperate shrub,Rhododendron weyrichii, which is distributed in the southwestern parts of the Japanese archipelago and on an island of South Korea, using statistical phylogeographic approaches based on the DNA sequences of two chloroplast and eight nuclear loci in samples analyzed from 18 populations on eight continental islands, and palaeodistribution modeling. Time estimates for four island populations indicate that the durations of vicariance history are different between these populations, and these events have continued since the last glacial or may have predated the last glacial. The constancy or expansion of population sizes on the Japanese islands, and in contrast a bottleneck in population size on the Korean island Jeju, suggests that these islands may have provided different conditions for sustaining populations. The result of palaeodistribution modeling indicates that the longitudinal range of the species as a whole has not changed greatly since the last glacial maximum. These results indicate that exposed seafloors during the glacial period formed both effective and ineffective migration corridors. These findings may shed light on the effects of seafloor exposure on the migration of plants distributed across continental islands.
authors.affiliation: Graduate School of Bioagricultural Sciences Nagoya University Nagoya Japan; Present address: Graduate School of Horticulture Chiba University Matsudo 648 Matsudo Chiba 271-8510 Japan.
authors.forename: Watanabe
authors.initials: W
authors.lastname: Yoichi
authors.affiliation: Gifu Academy of Forest Science and Culture Mino Gifu Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tamaki
authors.affiliation: Graduate School of Human and Environmental Studies Kyoto University Kyoto Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Sakaguchi
authors.affiliation: Department of Biological Science College of Natural Sciences Andong National University Andong Gyeongbuk Korea.
authors.forename: Jong-Suk
authors.initials: JS
authors.lastname: Song
authors.affiliation: Okayama University Okayama Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Bioagricultural Sciences Nagoya University Nagoya Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tomaru
keywords: ecological niche modeling; historical vicariance; island biogeography; isolation with migration model; population demography