A new species of Ponerorchis (Orchidaceae, Orchideae) from Xizang, China

A new orchid species Ponerorchis milinensis, from Milin County, Xizang of China is described here on the basis of morphological characters and molecular phylogenetics. Ponerorchis milinensis is morphologically close to P. nana but readily distinguished from it by a set of vegetative and reproductive characters, including its plant size, the number of leaves per stem, size of flowers, lip features, and spur shape. Molecular phylogenetic study using two nuclear markers (nrITS and Xdh) and three plastid markers (matK, psbA-trnH, and trnL-F) showed that P. milinensis formed a clade with P. tibetica and P. farreri. Ponerorchis milinensis differs from the latter two species by having a 3-lobed lip, two calli at the entrance of spur and 3-lobed stigma.