Spiranthes hongkongensis S. Y. Hu & Barretto (Orchidaceae): Newly Discovered Orchid on Ishigaki Island, Ryukyu Islands, Japan

lecular analyses of the internal transcribed spacer (ITS) and trnL–F intergenic spacer regions from such plants suggest that they are glabrous variants of S. australis, rather than range extensions of S. sinensis (Hayakawa et al. 2013, Suetsugu & Hayakawa 2016). During a herbarium investigation in KPM, we unexpectedly discovered a puberulous specimen of Spiranthes collected on Ishigaki Island in the southern Ryukyus, Japan. Since the feature ‘puberulous’ is often used as a diagnostic trait (Maekawa 1971, Satomi 1982), we considered these plants to be a range extension of S. australis. Since S. sinensis and S. australis vary greatly in their geographical distribution (Maekawa 1971, Satomi 1982, Hayakawa et al. 2013, Suetsugu & Hayakawa 2016), we also considered that the puberulous plant from Ishigaki may be a hairy variant of S. sinensis. Furthermore, considering that other taxa within the S. sinensis complex have been recognized in Taiwan, which is close to Ishigaki Island (Chung 2015, Hsu & Chung 2016, Pace et al. 2019), it was possible that Spiranthes L. C. Rich. (Orchidaceae) comprises ca. 50 species that are widely distributed across tropical and temperate regions of the Americas, Eurasia and Australia (Dueck et al. 2014, Surveswaran et al. 2017, 2018, Pace et al. 2019). The identification of species within the genus is often complicated because of morphological polymorphism. Within the S. sinensis species complex, pubescence of the inflorescence, stems and ovaries has been used diagnostically to distinguish between the closely related species, S. australis (R. Br.) Lindl. [syn. Spiranthes sinensis var. australis (R.Br.) H. Hara & S. Kitam. and Spiranthes sinensis var. amoena (M.Bieb.) H. Hara] and S. sinensis s.s. (Tsukaya 1994, 2005, Pace et al. 2019). These two species vary greatly in their geographic distribution, at least in Japan and Taiwan. In general, S. australis is mainly on the Japanese mainland (northern Ryukyus and northward), whereas S. sinensis is restricted to the central and southern Ryukyus, Japan and Taiwan (Maekawa 1971, Satomi 1982). Glabrous specimens of Spiranthes have rarely Acta Phytotax. Geobot. 70 (3): 205–208 (2019) doi: 10.18942/apg.201905 ISSN 1346-7565