New subtribe Pachitinae (Orchideae) of Orchidaceae: Evidence from morphological and molecular analyses

The subtribal delimitation and relationships of Orchideae remain unresolved. In the present study, the phylogenetic relationships among all subtribes of Orchideae were reconstructed, utilizing five plastid and two nuclear DNA sequences (rbcL, trnS-trnG, matK, trnL-F, psbA-trnH, Xdh and ITS) from 178 taxa of Orchideae. The combined results show that most clades are successively sister to the grade of clades representing antecedently accepted subtribes, but Pachites and Huttonaea do not belong to the previous classification of Disinae. In contrast, these two genera represent two additional isolated lineages. On this basis, a new subtribe, Pachitinae, is tentatively proposed to accommodate this taxon. Also, the subtribe Huttonaeinae Schltr. was recovered (1926: 568). In addition to the taxonomic treatment of this subtribe, the delimitation of many related subtribes in Orchideae is discussed.