Phylogenetic placement, taxonomic revision and a new species of Nothostele (Orchidaceae), an enigmatic genus endemic to the cerrado of central Brazil

Abstract

Nothostele is a rare genus endemic to central Brazil. The taxonomy of the genus is controversial and almost every taxonomist has had a different point of view regarding its generic and subtribal classification. After the first collection 138 years ago, N. acianthiformis has been collected again and we report here a phylogenetic analysis of the genus based on nuclear ribosomal internal transcribed spacer and plastid matK and trnL-trnF sequence data. Our results show that Nothostele belongs to subtribe Spiranthinae and is sister to Eltroplectris within the Stenorrhynchos clade. A reanalysis of gynostemium morphology shows that the presence of a hamulus was misinterpreted in Nothostele and that the placement of the genus in Cranichidinae based on morphology of the pollinarium is unwarranted. Furthermore, the flattened, sessile, prostrate leaves of N. acianthiformis, which are described here for the first time, occur in some Spiranthinae but are atypical in Cranichidinae. Specimens from Brasília in the Brazilian central plateau are a distinct new species, which is described here as N. brasiliaënsis. Currently, the genus comprises two disjunct species restricted to the cerrado and rocky field vegetation of central Brazil. © 2011 The Linnean Society of London.