A Molecular Phylogenetic Study of Lonicera L. (Caprifoliaceae) in Japan Based on Chloroplast DNA Sequences

Despite previous phylogenetic studies, the relationships among sections, subsections and species of Lonicera (Caprifoliaceae), especially in Japan, remain unclear. In this context, we investigated the phylogenetic relationships among 23 Japanese species belonging to all four sections and five subsections of Lonicera based on sequences of five chloroplast non-coding regions, rpoB-trnC, atpB-rbcL, trnS-trnG, petN-psbM, psbM-trnD. The trees obtained from were fundamentally identical with those reported previously, but provide some new insights on the Japanese species. 1) All Japanese species of Lonicera concerned here are assignable to one clade, corresponding to subgenus Lonicera sensu Hara. 2) Both sections Caeruleae and Lonicera are monophyletic, while neither section Nintooa nor Ishika is monophyletic. 3) Within section Ishika, each of the four subsections, Ishika, Monanthae, Bracteatae and Rhodanthae forms a clade, although the branch supports for certain clades are weak. 4) Subsection Purpurascentes is a polyphyletic group. Two Japanese species, Lonicera ramosissima and L. linderifolia form a clade with weak support, but the other species of subsection Purpurascentes distributed in China form the other clade. 5) Subsection Rhodanthae is more closely related to sections Nintooa and Lonicera than to other subsections. Based on the results, the circumscription of the higher taxonomic groups for the Japanese species of Lonicera proposed by Hara in 1983 is fundamentally acceptable.