An Elegy to Rangaeris, Including a Description of Two New Genera in the Cyrtorchis–Tridactyle Clade (Orchidaceae, Angraecinae)

Abstract

The phylogenetic position of Rangaeris (Schltr.) Summerh. has been one of the most problematic issues of angraecoid orchid taxonomy. A recently published phylogenetic tree with nearly comprehensive taxon sampling of African angraecoid orchids suggested that this genus was polyphyletic, as its species appear nested within different subclades of the Cyrtorchis–Tridactyle clade. However, the lack of DNA data for the generic type, R. muscicola (Rchb. f.) Summerh., and for the little-known species R. longicaudata (Rolfe) Summerh. and R. trilobata Summerh., has precluded an integrative reappraisal of the delimitation of this genus. Here we present the results of a new phylogenetic analysis of one nuclear (ITS) and five plastid markers (matK, rps16, trnC-petN intergenic spacer, trnL-trnF intergenic spacer, ycf1) for all six species of Rangaeris, including those recently transferred to Podangis Schltr. and Ypsilopus Summerh., together with a representative sampling of 14 other species of the genera Cyrtorchis Schltr., Listrostachys Rchb. f., Plectrelminthus Raf., Summerhayesia P. J. Cribb, Tridactyle Schltr., and Ypsilopus. Based on molecular and morphological evidence, R. muscicola is transferred to Podangis, where Rangaeris is reduced to the rank of section. In addition, R. longicaudata and R. trilobata are each moved to new monotypic genera, Planetangis Stévart & Farminhão and Aziza Farminhão & D’haijère, respectively. An identification key for all genera of the Cyrtorchis–Tridactyle clade is presented, together with one for the three species of recircumscribed Podangis. Finally, taxonomic accounts of the new genera are presented, including amended descriptions, illustrations, distribution maps, and preliminary conservation status assessments of their species.