Phylogenetics of Cranichideae with emphasis on Spiranthinae (Orchidaceae, Orchidoideae): evidence from plastid and nuclear DNA sequences.

DNA sequences from plastid rbcL and matK genes and the trnL-F region, as well as the nuclear ribosomal ITS region, were used to evaluate monophyly and subtribal delimitation of Cranichideae and generic relationships in Spiranthinae. Cranichideae are moderately supported as monophyletic, with Chloraeinae and Pterostylis-Megastylis indicated as their collective sisters. Within Cranichideae, Pachyplectroninae and Goodyerinae form a well-supported monophyletic group sister to a "core spiranthid" clade that includes, according to their branching order, Galeottiellinae, Manniellinae, and a Prescottiinae-Cranichidinae-Spiranthinae subclade. Inclusion of Galeottiella in Spiranthinae, as in previous classifications, renders the latter paraphyletic to all other spiranthid subtribes. Cranichidinae and Spiranthinae (minus Galeottiella) are monophyletic and strongly supported, but Prescottiinae form a grade that includes a strongly supported prescottioid Andean clade and a weakly supported Prescottia-Cranichidinae clade sister to Spiranthinae. Well-supported major clades in Spiranthinae identified in this study do not correspond to previous alliances or the narrowly defined subtribes in which they have been divided recently. Morphological characters, especially those that have been used for taxonomic delimitation in Cranichideae, are discussed against the framework of the molecular trees, emphasizing putative synapomorphies and problems derived from lack of information or inadequate interpretation of the characters.