Two new species of Oreocharis (Gesneriaceae) from Fan Si Pan, the highest mountain in Vietnam

Two new species of Oreocharis Benth. from Fan Si Pan, the highest mountain in Vietnam (Sa Pa) are described and illustrated.

Fan Si Pan is a species-rich diversity hotspot in Indochina, the flora of which is still incompletely known. Fan Si Pan (in Vietnamese: Phan Xi Pang), the highest mountain in Vietnam (3143 m elevation), is situated in the northwest of the country and its orogeny is linked to the Himalayan Mountain chain It also has the highest recorded levels of biodiversity in Indo-China and is part of one of the 25 world’s biodiversity hotspots.

The genus is distributed predominantly in China, with few species in Thailand, Myanmar, Bhutan, NE India, Japan and Vietnam. Most Oreocharis species occur in relatively restricted and geographically isolated localities with very few widely distributed. No new species of Oreocharis were described from Vietnam from 1908 until recently when three new species were discovered.

During a joint Sino-Vietnamese botanical survey in Fan Si Pan in November 2012, two of the authors (QHN and YMS) collected several specimens of Gesneriaceae. These included two collections of fruiting specimens. From the vegetative habit and fruit characters, they were identified as belonging to Oreocharis. In September 2013, cultivated plants of the two collections produced flowers unlike any of the described species in the genus. After consulting the relevant literature from China and Vietnam, it was confirmed that the two species were new to science. On examination of other recent and historic unidentified collections from Vietnam, a number of other specimens of one of the species were also found. Here, they are described and illustrated via photography and drawings.

 Oreocharis grandiflora W.H.Chen, Q.H.Nguyen & Y.M.Shui, is similar to O. flavida Merr. from Hainan province, China, but differs mainly by its larger and infundibuliform corolla, stamens adnate to the base of the corolla tube and stamens coherent in two pairs. The second, Oreocharis longituba W.H.Chen, Q.H.Nguyen & Y.M.Shui, is similar to O. hirsuta Barnett, endemic to northern Thailand, but mainly differs in its pubescence, coherent stamens and glabrous filaments.

This work was supported by projects of the “The National Natural Science Foundation of China”(grant no. 31470306, 31000258), Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Y4Zk111B01) and “Key Laboratory of Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, the Chinese Academy of Sciences” (grant no. 2014CB954100). The result published as " Two new species of Oreocharis (Gesneriaceae) from Fan Si Pan, the highest mountain in Vietnam" on PhytoKeys.

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Oreocharis grandiflora W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (A–F) and O. flavida Merr. (G–I)

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Oreocharis longituba W.H.Chen, Q.H.Nguyen & Y.M.Shui, sp. nov. (A–H) and its most similar species, Oreocharis hirsuta Barnett (I–L)