Liparisnapoensis (Orchidaceae), a new species from Guangxi, China

Abstract Liparisnapoensis, a new orchid species belonging to section Cestichis from Guangxi, China is described and illustrated. It occurs in the karst limestone forest. The new species is morphologically similar to L.viridiflora and L.somae, but can be readily distinguished by having narrowly oblong-falcate petals; flabellate-quadrate lip distinctly concave at base and emarginate at apex; conspicuously arcuate column with a pair of wedge-shaped wings.


Introduction
The genus Liparis L.C. Richard (1817: 21), also known as false twayblade, belongs to the tribe Malaxideae of the subfamily Epidendroideae. It comprises about 320 species with cosmopolitan distribution from the tropics and subtropics to the temperate and alpine regions (Pearce andCribb 2002, Pridgeon et al. 2005). Since its publica-tion, various segregate genera have been proposed such as Alatiliparis Marg. & Szlach. (2001: 78), Disticholiparis Marg. & Szlach. (2004: 175), Seidenforchis Marg. (2006 and Platystyliparis Marg. (2007: 35). Molecular phylogenetic studies indicated that Liparis in broad delimitation is polyphyletic (Cameron 2005, Li andYan 2013). Pridgeon et al. (2005) concluded that Liparis sensu stricto should be restricted to a group of temperate Asian species with the type, L. loeselii (L.) Richard. It is as yet unclear whether the recognition of these splits provides a better taxonomy, thus we opted to maintain Liparis as a broad concept for the present.
As traditionally delimited, Liparis section Cestichis Thouars ex Lindley (1831: 29) is characterised by having coriaceous, non-plicate leaves. They are usually epiphytes with distinct pseudobulbs and occur mainly in tropical Asia. In China, the genus Liparis is represented by about 70 species (Chen et al. 2009), including eight recently described species (see Jin 2011, Wu et al. 2012, Hsu 2013, Li and Yan 2013, Su et al. 2015, Tang et al. 2015. More than half of the Chinese Liparis species (40, about 57%) belong to section Cestichis.
The limestone karst area is part of a global biodiversity hotspot. Floristic investigations of limestone areas in southwestern Guangxi, China from April 2012 to July 2015, have yielded the discovery of an interesting Liparis species of section Cestichis. Morphologically, this species is superficially similar in appearance to L. viridiflora (Blume) Lindley (1831: 31) in vegetative habit, but differs significantly from the latter in the floral morphology. On the other hand, it bears yellowish or whitish flowers somewhat resembling those of L. somae Hayata (1914: 33), a rare species endemic to Taiwan, but several critical details differ. Over the past three years, the living and cultivated specimens were monitored in the field and in the nursery of South China Botanical Garden (SCBG), Chinese Academy of Sciences (CAS). Careful examinations of diagnostic morphological features of similar taxa and literature surveys (Seidenfaden 1976, Comber 1990, Yang 2006, Averyanov 2013, 2015, Tang et al. 2015 indicated that it represents a species new to science and accordingly described herein.

Materials and method
A total of 450 herbarium specimens of Liparis species in the section Cestichis were examined from herbaria BM, E, HN, IBK, IBSC, K, PE and US (acronyms according to Thiers 2018). The taxonomic status of Liparis napoensis and its close allies were examined by checking the type specimens in these herbaria and online digital image repositories and databases available on JSTOR Global Plants website (http:// plants.jstor.org). Relevant literature, including protologue was consulted. Morphological descriptions and measurements of the putative new species were undertaken based on three living specimens in cultivation (South China Botanical Garden). The specimens were observed and photographed under a stereomicroscope (Olympus MD-90). The conservation status of the new species was evaluated following the guidelines in IUCN (2017).

Taxonomic description
Liparis napoensis L. Li Diagnosis. Liparis napoensis differs from its closest allies: L. viridiflora and L. somae in the clustered ovoid-cylindrical or narrowly pyriform pseudobulbs, narrowly oblongfalcate petals; a flabellate-quadrate lip with a distinctly concave base, an emarginate apex and erose margins; a conspicuously arcuate column with a pair of wedge-shaped wings.
Distribution and habitat. Endemic to Guangxi in China. Lithophytes in rocks crevices where soil or organic matter has accumulated at elevations from ca. 650 m to 900 m in karst limestone forest.
Etymology. The epithet "napoensis" is derived from the type locality: Napo County, Guangxi, located at China's southwest border, where the species was discovered.
Phenology. Flowering and fruiting in January-February. Conservation status. Based on careful field investigations in the past years, this species is rare and only known from the type locality. Plants grow in sparsely scattered  groups and the known population of two colonies consists of only a few dozen individuals (density less than one plant per 20 m 2 ). In addition, the location is not in a protected area and accessible to casual hikers. According to the guidelines for using the IUCN Red List Categories and Criteria (IUCN 2017), the species is categorised as Critically Endangered [CR B2ab(iii)] due to its rarity and the threat of disturbance.
Taxonomic notes. The new species in its general appearance has some superficial similarity with Liparis viridiflora, but the latter differs in longer petioles, narrowly linear petals, ovate-oblong lip with a mucronate tipped apex and a column with rounded wings. It also superficially resembles L. somae, but is characterised by having ovoidcylindrical or narrowly pyriform pseudobulbs, a flabellate-quadrate lip with a distinctly concave base and an emarginate apex. A detailed morphological comparison between L. napoensis and its closely related taxa L. viridiflora and L. somae is presented in Table 1.