Endemic dwarf birch Betula apoiensis (Betulaceae) is a hybrid that originated from Betula ermanii and Betula ovalifolia

Abstract

Betula apoiensis (Betulaceae), a tetraploid endemic to Mount Apoi in Hokkaido, is endangered in Japan. To reveal the origin of this species, the internal transcribed spacers and 5.8S gene of nuclear ribosomal DNA (ITS + 5.8S) and a microsatellite with its flanking region of nuclear DNA (Bp09) were sequenced and their haplotypes were determined for 12 Betula species in the Sakhalin, Hokkaido and Honshu Islands. The most parsimonious trees of ITS + 5.8S and Bp09 haplotypes had different topologies and no clades were consistent between the two trees. In both ITS + 5.8S and Bp09, B. apoiensis shared identical haplotypes with Betula ermanii and Betula ovalifolia, and had haplotypes that appeared to have been derived from each of the two species. This result suggests that B. apoiensis originated from hybridization between B. ermanii and B. ovalifolia. © 2006 The Authors.