Phylogeny of South American Pogonieae (Orchidaceae, Vanilloideae) based on sequences of nuclear ribosomal (ITS) and chloroplast (psaB, rbcL, rps16, and trnL-F) DNA, with emphasis on Cleistes and discussion of biogeographic implications

Tribe Pogonieae (Orchidaceae), as currently known, comprises five genera distributed from South to North America and Eastern Asia. Phylogenetic inferences within Cleistes and among genera of tribe Pogonieae were made based on nrDNA (ITS) and cpDNA (trnL-F, rps16, rbcL, and psaB) sequence data and maximum parsimony. Eighteen species of Cleistes, members of all other genera of Pogonieae, and outgroups were sampled. Analyses based on individual DNA regions provided similar topologies. All evidence indicates that Cleistes is paraphyletic. The North American C. divaricata and C. bifaria are more closely related to the temperate genera Isotria and Pogonia than to their Central and South American congeners, the latter constituting a monophyletic group characterized by the production of nectar as reward, tuberous roots, and their distribution in Central and South America. The Amazonian Duckeella is sister to the remainder of Pogonieae. Taxonomic and biogeographic implications are discussed, and morphological synapomorphies are given for clades obtained in the inferred molecular phylogeny.