Photosystem II gene sequences of psbB and psbC clarify the phylogenetic position of Vanilla (Vanilloideae, Orchidaceae)

Nucleotide sequences of the plastid genes psbB and psbC were obtained for 34 taxa to represent most genera currently classified within Vanilloideae (Orchidaceae). These genes code for two of the subunits that make up the Photosystem II protein P680, and have only rarely been used for reconstructing phylogenetic relationships among plants. We failed to amplify psbB from the achlorophyllous genera Cyrtosia and Lecanorchis, but were able to align full length copies of psbC sequences from two species of Cyrtosia with the other taxa. This was not the case for an anomalous psbC sequence obtained for Lecanorchis. Nucleotide variation within each of these genes is sufficient to resolve the major relationships among Vanilloideae, and the combined two-gene tree is fully resolved at the genus level and highly supported. These gene trees demonstrate with a high degree of confidence (95% jackknife support) that a clade of mostly achlorophyllous tropical vines including Pseudovanilla and Erythrorchis are the sister group to Vanilla. The two New Caledonian endemic genera of Vanilloideae are sister to this pair, and Epistephium is sister to all remaining Vanillieae. (c) The Willi Hennig Society 2006.