Diphtherophyllon, a New Genus of Spiranthinae (Orchidaceae) from North- and Central America and the Greater Antilles, with Description of a New Species From the Chihuahuan Desert. NEW GENUS AND SPECIES OF SPIRANTHINAE ORCHIDS

A new orchid species from the Chihuahuan Desert realm in Tamaulipas, Mexico and Texas, U.S.A, is described and illustrated. The phylogenetic position of the new species was assessed by a cladistic parsimony analysis of non-coding nuclear (ITS) and plastid (trnL-trnF) DNA sequences of 60 species/35 genera of Spiranthinae and 15 additional species and genera of Cranichideae. The results indicate a close relationship of the new species to several species previously included in Schiedeella, especially S. wercklei, but our analysis also shows that such a group does not belong to the clade that includes the type species of Schiedeella (S. transversalis), being instead sister to Mesadenus. A new genus, Diphtherophyllon, is proposed to include the new species (D. deserticolum) and its closest relatives (D. micranthum var. micranthum, D. micranthum var. garayanum, D. wercklei). The identity of Lexarza’s Neottia micrantha is clarified, additional species belonging in this clade are discussed, and the required transfers made. An identification key to the three species and two varieties we recognize in the new genus is provided