Molecular phylogeny and taxonomic synopsis of the angraecoid genus Ypsilopus (Orchidaceae, Vandeae)

Previous phylogenetic analyses focused on angraecoid orchids suggested that the genus Ypsilopus was paraphyletic and that some species of Tridactyle and Rangaeris belong to a clade that included Ypsilopus. These studies, based on three to four genes, sampled few taxa in each genus, and did not include the type of Rangaeris, nor did they take morphological variation into account. To delineate Ypsilopus more precisely, we reconstructed phylogenetic relationships of the genus and seven other closely related genera by analysing sequence variation at the nuclear ribosomal internal transcribed spacer (ITS-1) and at five plastid markers (matK, rps16, trnC-petN intergenic spacer, trnL-trnF intergenic spacer, ycf1), from 42 specimens representing 36 taxa. Trees based on maximum likelihood and Bayesian inference confirm that two species of Tridactyle are nested with three Ypsilopus species, including the type of the latter, and two species of Rangaeris are grouped with this clade. Moreover, we examined morphological variation among all species belonging to these three genera, highlighting morphological features that characterize Ypsilopus, and we used these data to assign the two species of Tridactyle included in the molecular analyses, three other species of Tridactyle not included in the molecular analyses and two species of Rangaeris to Ypsilopus. New combinations for Tridactyle citrina, T. furcistipes, T. sarcodantha, T. tanneri, T. tricuspis, Rangaeris amaniensis and R. schliebenii in Ypsilopus are thus proposed, and one new section (i.e., Ypsilopus sect. Barombiella) is described. Keys to the species of Ypsilopus and closely related genera are provided, along with a table of characters that can be used to differentiate these species.