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| Ophiorrhiza xishuiensis Sheng H.Tang, Jia W.Yang & X.Z.He, in He, Dai, Xu, Yang et Tang, 2026. |
Abstract
A new species in Rubiaceae, Ophiorrhiza xishuiensis, is described from China. The new species is endemic to the Danxia landform at the juncture of Guizhou Province, Sichuan Province, and Chongqing City. It is a herb with a 1–7 cm long rooting stem, 3–11 nodes, and most leaves arranged in markedly unequal pairs. It has a somewhat inequilateral leaf blade base, a congested-cymose inflorescence, and well-developed bracteoles. We investigated two populations in Guizhou, China. The new taxon has been collected or photographed by others in Sichuan and Chongqing, China, and misidentified as O. japonica, O. umbricola, O. cantonensis, or O. chinensis. An identification key to O. xishuiensis and morphologically similar species is provided.
Key words: Danxia landform, flora of China, new taxon, Ophiorrhiza
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| Habitat of Ophiorrhiza xishuiensis sp. nov. A, B. Population of Sanchahe Town, Xishui County, China; C, D. Population of Baoyuan Town, Chishui City, China (Photographed by Sheng-Hu Tang and Xuan-Ze He). |
Ophiorrhiza xishuiensis Sheng H.Tang, Jia W.Yang & X.Z.He, sp. nov.
Diagnosis. The new species is most similar to O. japonica, O. guizhouensis, and O. chinensis by the length of the stipules, calyx lobes and corolla tube, the shape of the corolla, and the distribution areas and altitudes. It differs from O. japonica and O. guizhouensis by the 1–7 cm long rooting stems (vs. 10–30 cm, or longer), the fact that most leaves are arranged in markedly unequal (vs. subequal) pairs, the style reaching above (vs. below) the middle of the tube in the short-styled flowers, and the glabrous (vs. pubescent) style in the long-styled flowers. It is distinct from O. chinensis by the congested-cymose (vs. paniculiform to cymose) inflorescences, the well-developed and persistent (vs. absent or reduced and caducous) bracteoles, and the glabrous (vs. pubescent) style in the long-styled flowers.
Xuan-Ze He, Zheng-Xian Dai, Jian Xu, Jia-Wen Yang and Sheng-Hu Tang. 2026. Ophiorrhiza xishuiensis (Rubiaceae), A New Species endemic to Guizhou, Sichuan, and Chongqing, China. PhytoKeys. 275: 163-176. DOI: doi.org/10.3897/phytokeys.275.189435 [29 May 2026]
