Phylogenetic analysis of Chloraeinae (Orchidaceae) based on plastid and nuclear DNA sequences

Abstract

The phylogenetic relationships of subtribe Chloraeinae, a group of terrestrial orchids endemic to southern South America, have not been satisfactorily investigated. A previous molecular phylogenetic analysis based on plastid DNA supported the monophyly of Chloraeinae and Gavilea, but showed that Chloraea is non-monophyletic and that the sole species of Bipinnula analysed is sister to Geoblasta. However, that analysis included only 18 of the 73 species belonging to this subtribe. Here, the phylogenetic relationships of Chloraeinae were assessed by analysing aproximately 7500 bp of nucleotide sequences from nuclear ribosomal internal transcribed spacer (ITS) and plastid DNA (rbcL, matK, trnL-trnF, rpoB-trnC) for 42 species representing all four currently accepted genera of Chloraeinae and appropriate outgroups. Nuclear and plastid data were analysed separately and in combination using two different methods, namely parsimony and Bayesian inference. Our analyses support the monophyly of Chloraeinae and their inclusion in an expanded concept of Cranichideae, but none of the genera of Chloraeinae that includes more than one species is monophyletic. Gavilea and Bipinnula are paraphyletic, with Chloraea chica nested in Gavilea and Geoblasta penicillata in Bipinnula. As currently delimited, Chloraea is polyphyletic. The taxonomic changes proposed recently are for the most part not justifiable on phylogenetic grounds, except for recognition of the monotypic genus Correorchis. The lack of resolution for the relationships among species of ‘core’Chloraea suggests a relatively recent diversification of this group. The current generic classification is in need or revision, but additional study is advisable before carrying out further taxonomic changes. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168, 258–277.