Primulina papillosa (Gesneriaceae), a new species from limestone areas of Guangxi, China

Abstract Primulina papillosa Z.B. Xin, W.C. Chou & F. Wen, a new species from limestone areas of Guangxi, China, is described and illustrated here. It morphologically resembles P. linearifolia (W.T. Wang) Yin Z. Wang and P. pseudolinearifolia W.B. Xu & K.F. Chung, but can be easily distinguished by some combined characters, especially its leaf blades densely papillose-hispid. We found only one population at the type locality with no more than 200 individuals, so that this new species is provisionally assessed as Critically Endangered (CR) using IUCN Criteria.


Introduction
By the end of 2020, the genus Primulina Hance (1883) of the family Gesneriaceae comprised 201 species and 27 varieties (IPNI 2021;Tropicos 2021). It is mainly distributed throughout southern, south-western China and northern Vietnam (Wang et al. 2011;Weber et al. 2011). China is the centre of diversity for Primulina with at least 183 species and 27 varieties occurring there at present, especially in limestone areas (e.g. Wei 2018;Wen et al. 2019Wen et al. , 2021Ge et al. 2020;Liu et al. 2020;Xin et al. 2020a, b, c). The tropical and subtropical karst limestone mountainous areas of Guangxi are the centres of species diversity and differentiation of this genus ). An acceleration of Primulina species discovery has been seen over the last five years, with an average of over ten new species per year (Wen et al. , 2021. Assuming this trend persists, more new Primulina species from China will most likely be discovered (Möller 2019).

Primulina papillosa
Phenology. Flowering from September to November, fruiting from October to December.
Etymology. The specific epithet 'papillosa' is derived from the leaf blade densely papillose-hispid on both surfaces. Vernacular name. The Chinese name '刺疣报春苣苔' (Cì Yóu Bào Chūn Jù Tái) is newly coined for this species because of its special leaf blades surface full of densely papillose-hispid hairs.
Distribution and habitat. Primulina papillosa is only known from the type locality, Dingdang Town, Longan County, Nanning City, Guangxi, China. It only grows in crevices of the cliff near the top of limestone hills in a subtropical evergreen seasonal rain forest.
Conservation status. Primulina papillosa is only found from the type population with less than 200 individuals. The EOO and AOO of the new species are about 1.05 km 2 and 0.01 km 2 , respectively. The beautiful flowers, thickened rhizomatous woody stem and leaves with dense papillose-hispid hairs, have led to its over-harvesting by local people who have sold it as an ornamental plant. Furthermore, the natural habitat is mostly disturbed due to local farmers imposing intense pressure on the remaining patches of primary forest. Thus, following the IUCN Red List Categories and Criteria (IUCN 2019), it is temporarily assessed as Critically Endangered [CR B1+B2ab (iii,v)].