Oreocharis tetrapterus (Gesneriaceae), a new species from East Guangxi, China

Abstract A new species, Oreocharis tetrapterus F.Wen, B.Pan & T.V.Do (Gesneriaceae) from Gupo Mountain area, Hezhou city, Guangxi Zhuangzu Autonomous Region, China, is described and illustrated. The new species has a zygomorphic tetramerous corolla with two adaxial and two abaxial lobes and two fertile stamens in the posterior position, making this a unique combination of floral characteristics in the expanded Oreocharis.


Introduction
In 2011, Oreocharis Bentham was redefined (Möller et al. 2011), and soon afterwards, this genus rapidly grew with the addition of many new species. Oreocharis sensu lato now comprises at least 125 species (Möller et al. 2016, Möller 2019. Oreocharis is quasi-endemic to China because there are about 14 species distributed in other countries apart from China: namely, O. primuloides (Miq.) Benth. & Hook.f. ex Clarke (Japan), O. hirsuta Barnett (Thailand), O. muscicola (Craib) Mich. Möller & A.Weber (Bhutan, India, Myanmar), O. longifolia (Craib) Mich. Möller & A.Weber (Myanmar) and nine species from Vietnam (Wang et al. 1990, 1998, Li and Wang 2004, Wei et al. 2010, Do et al. 2017, Chen et al. 2017, Möller 2019. A joint expedition from the Gesneriad Conservation Center of China (GCCC), Guilin Botanical Garden and Vietnam National Museum of Nature yielded collections of flowering specimens and living plants of an unidentified species of Gesneriaceae in August 2016. Plants raised in cultivation in the GCCC greenhouse from these collected living plants and seeds flowered in 2018. We carefully observed its habit (leaves in basal rosette), flower shape (infundibuliform corolla), number of fertile stamens (two, free, in the posterior position), filament shape (nearly straight) and capsule shape (long and cylindrical bivalved capsules with loculicidal dehiscenc), and identified it as belonging to the expanded Oreocharis (Wang et al. 1990(Wang et al. , 1998Möller et al. 2011). The expanded Oreocharis includes species of the former Opithandra B.L. Burtt (Burtt 1958) that were characterized by two stamens in the posterior position similar to the new species described here (Möller et al. 2011).
Following a careful review of the relevant herbarium specimens and taxonomic publications of Oreocharis from Guangxi and adjacent regions, we concluded that this species is new to science. The unusual characteristics of two stamens and zygomorphic flower with 2-lobed upper and lower lips are very rare in the expanded Oreocharis. Oreocharis tetrapterus F. Wen, B. Pan & T.V. Do is described and illustrated below.
Etymology. The specific epithet, 'tetrapterus' from the Greek meaning having four wings or wing-like appendages. Here it refers to the four 'wing-like' lobes of the corolla, with adaxial and abaxial lips both having 2 lobes., Vernacular name. The Chinese name of this new species is 姑婆山马铃苣苔. The pronunciation of the Chinese of this species is 'Gū Pó Shān Mǎ Líng Jù Tái'.
Distribution and ecology. Oreocharis tetrapterus is currently known only from one population of ca. 50 individuals at the type locality. The species may be endangered, but more data is needed to evaluate this reliably. The species grows on moist surfaces, on moss-covered granite rocks with other plants under subtropical bamboo and evergreen broad-leaved forest cover in Hezhou City, Guangxi.
Notes. We understand most other Gesneriaceae with two stamens have them in the anterior position, but this special character, two stamens in the posterior position, has also evolved outside the Oerocharis s. l. in the South American Sarmienta Ruiz & Pavon   . Oreocharis tetrapterus is morphologically unique within Oreocharis s. l. and can be easily distinguished from the other species with four lobes by its zygomorphic corolla, whereas the others are actinomorphic, for example O. sinensis and O. esquirolii (O. esquirolii also has 5-lobed corolla type, occasionally) (Fig. 4).