Geographical origin of Leucobryum boninense Sull. & Lesq. (Leucobryaceae, Musci) endemic to the Bonin Islands, Japan.

Leucobryum boninense is endemic to the Bonin Islands, Japan, and its related species are widely distributed in Asia and the Pacific. We aimed to clarify the phylogeneticrelationships among Leucobryum species and infer the origin of L. boninense. We also describe the utility of the chloroplast trnK intronincluding matK for resolving the phylogeneticrelationships among Leucobryum species, as phylogeneticanalyses using trnK intronand/or matK have not been performed well in bryophytesto date. Fifty samples containing 15 species of Leucobryum from Asia and the Pacific were examined for six chloroplast DNAregions including rbcL, rps4, partial 5′ trnK intron, matK, partial 3′ trnK intron, and trnL-F intergenic spacer plus one nuclear DNA region including ITS. A molecular phylogenetictree showed that L. boninense made a clade with L. scabrum from Japan, Taiwan and, Hong Kong; L. javense which is widely distributed in East and Southeast Asia, and L. pachyphyllumand L. seemannii restricted to the Hawaii Islands, as well as with L. scaberulum from the Ryukyus, Japan, Taiwan, and southeastern China. Leucobryum boninense from various islands of the Bonin Islands made a monophylic group that was closely related to L. scabrum and L. javense from Japan. Therefore, L. boninense may have evolved from L. scabrum from Japan, Taiwan, or Hong Kong, or L. javense from Japan. We also described the utility of trnK intronincluding matK. A percentage of the parsimony-informative characters in trnK intronsequence data (5.8%) was significantly higher than that from other chloroplast regions, rbcL (2.4%) and rps4 (3.2%) sequence data. Nucleotide sequence data of the trnK intronincluding matK are more informative than other chloroplast DNAregions for identifying the phylogeneticrelationships among Leucobryum species.