Chloroplast DNA phylogeny of subtribe Dendrobiinae (Orchidaceae): Insights from a combined analysis based on rbcL sequences and restriction site variation

Phylogenetic analyses using two chloroplast DNA data sets, derived from variation of the ribulose-bisphosphate carboxylase gene (rbcL) and restriction sites, were performed to examine relationships among 13 taxa in subtribe Dendrobiinae, one of the most taxonomically complicated groups in Orchidaceae, and its putative sister groups. Owing to a limited number of informative substitutions, the rbcL data set did not provide conclusive evidence in itself. The data set combining rbcL and restriction site mutations, however, provided the following insights: (1) Pseuderia belongs with tribe Podochileae rather than tribe Dendrobieae. (2) Subtribe Dendrobiinae is monophyletic a Pseuderia is excluded. (3) Excluding Pseuderia, Dendrobiinae comprises three major clades: Clade 1 (Dendrobium section Spatulata, Cadetia, Diplocaulobium, and Flickingeria); Clade 2 (Dendrobium sections Dendrobium and Callista); and Clade 3 (Epigeneium). (4) Epigeneium diverged early from the lineage including Clades 1 and 2. (5) Relative to Cadetia, Diplocaulobium, and Flickingeria, Dendrobium is shown to be para-/polyphyletic. (6) Diplocaulobium and Flickingeria constitute a monophyletic clade, from which clade Dendrobium section Spatulata and Cadetia form successive sister groups. Among these results, (1) and (5) are especially stable in view of the congruence between the separate and combined analyses as well as robust internal support.