A molecular phylogeny of the subtribe Pterostylidinae (Orchidaceae): resolving the taxonomic confusion

Abstract

In the past decade, two major classification schemes of the subtribe Pterostylidinae have resulted in taxonomic confusion because a single well known genus was split into a large number of new genera and subgenera, many of which are difficult to discriminate accurately. These classifications have not been accepted widely among systematists because of poor phylogenetic support for several genera. Analyses of the internal transcribed spacer (ITS) region of nuclear rDNA in a large number of species and samples facilitate further clarification of the relationships within the Pterostylidinae. The phylogenetic trees were reconstructed using parsimony and Bayesian methods. These phylogenetic trees indicate that subtribe Pterostylidinae is monophyletic, and support the concept of a single genus, Pterostylis R.Br. sensu lato within the Pterostylidinae. Two clades representing subgenera correlate with the morphology of the lateral sepals, whereas several of the previously erected genera consistently have poor support. The proposed subgenera are divided further into 10 sections. Several closely related taxa with identical ITS sequences require further scrutiny by population-level molecular techniques to determine their taxonomic status.