Molecular phylogeny of the genus Pieris (Ericaceae) with special reference to phylogenetic relationships of insular plants on the Ryukyu Islands

Abstract

Phylogenetic relationships within the genus Pieris (Ericaceae) were investigated based on the rbcL and matK genes along with five spacer sequences of chloroplast DNA to address questions regarding the phylogeography of the genus in association with insular plants on the Ryukyu Islands. The most parsimonious trees indicated that P. floribunda from eastern North America is a sister taxon to the remaining taxa examined, and suggested that the East Asian taxa examined are monophyletic. A morphologically cohesive group, section Pieris, was revealed to be paraphyletic. Within the East Asian clade, insular endemics from the Ryukyu Islands, Taiwan, and mainland Japan formed a sister group to P. formosa from the Himalayas and southern China. Our data suggest that the insular endemics of the Ryukyu Islands and Taiwan arose via allopatric divergence as a result of a paleogeographical land configuration of a landbridge during the early–middle Pleistocene in the Quaternary Period.