The taxonomic identity of three varieties of Lecanorchis nigricans (Vanilleae, Vanilloideae, Orchidaceae) in Japan.

To elucidate the taxonomy of the Lecanorchis nigricans Honda, 1931 species complex, the present study investigated the detailed morphology of three L. nigricans varieties in Japan. While L. nigricans var. patipetala Y.Sawa, 1980 and L. nigricans var. yakusimensis T.Hashim., 1990 have often been treated as synonyms of L. nigricans var. nigricans, the present study demonstrates that the three varieties are morphologically distinct. More specifically, L. nigricans var. nigricans only produces complete cleistogamous flowers and is distinct from the plants currently called "L. nigricans", which are identical to the chasmogamous variety L. nigricans var. patipetala. The other chasmogamous variety L. nigricans var. yakusimensis can be easily distinguished from L. nigricans var. patipetala by its more spatulate tepals and higher cucullate lip. Therefore, the present study provides emended description of the three L. nigricans varieties based on type specimens and specimens collected from type localities. In addition, the isotype specimen of L. nigricans var. patipetala is designated as the lectotype because the holotype has been lost.