The genus Primulina Hance (Hance, 1883) has become the largest genus of Gesneriaceae in China, following generic recircumscriptions based on recent molecular phylogenetic analyses (Wang et al., 2011; Weber et al., 2011; Xu et al., 2019) . The newly revised Primulina consists of 230 species (excluding infraspecific taxa) primarily distributed from South and Southwest China to North Vietnam (GRC, 2023; Wen et al., 2019, 2021) . Up to date, there are213 accepted species (excluding infraspecific taxa) of Primulina recorded from China (GRC, 2023; Wen et al., 2021) . The tropical and subtropical limestone mountainous areas of Guangxi, China, are the centers of species diversity and diversification of this genus (Li et al., 2019) . Many new taxa of Primulina from South and Southwest China have been discovering and publishing since two decades (Guo et al., 2015; Möller, 2019; Wen et al., 2021) . In the past decade, the number of new species in Primulina has averagely increased by about 10 per year (Xu et al., 2017) . In the course of a floristic survey of limestone areas in July 2020, we discovered a rare plant of Gesneriaceae from Pingguo City, Guangxi, China. The species is recognized as Primulina by the following characters: the single chiritoid stigma, where the upper lobe of the stigma is not developed (Wang et al., 2011; Weber et al., 2011) . After consulting the relevant literature (Xu et al., 2012; Wen et al., 2014; Guo et al., 2015; Möller et al., 2016; Ma et al., 2017; Li et al., 2019; Zhang et al., 2021) , as well as detailed comparison with relevant specimens and taxonomic publications (Wang et al., 1998; Li &Wang, 2005; Wei et al., 2010; Wang et al., 2017) , a new species of Primulina is identified, which is described and illustrated below.

Primulina pingguoensis H.S. Ma &B. Pan, sp. nov. (Fig.1, Fig.2)

The new species is similar to Primulina carinata Y. G. Wei, F. Wen &H. Z. Lü in floral characteristics, but it differs from the latter by lobes narrowly lanceolate-linear, length-width ratio more than 2 (rounded-ovate, length-width ratio less than 1.5) , 8-10 purple stripes from corolla throat to the bottom of corolla tube, without honey guides (vs. brown stripes, 2 yellow honey guides inside, leaf blade elliptic to broadly ovate, (6.5-9.5) cm × (4.5-6.5) cm [vs. broadly elliptic to ovate, (4.0-5.0) cm × (3.0-4.0) cm], leaf blade base slightly cuneate (vs. rounded) , corolla tube tubular, ventrally carinate, (vs. narrowly funnelform, strongly carinate, forming a clear keel) , etc.

Type: CHINA, Guangxi, Pingguo City, Guohua Town, Longyang Village, elevation 220 m, 23°16′ N, 107°29′ E, 20 July 2020, Hu-Sheng Ma &Bo Pan MHS2020072001 (Holotype: IBK!, Isotypes: PE! and IBK!) .

1 Description

Perennial herbs. Rhizomatous stem subterete, 1-4 cm long, ca.9 mm in diameter. Leaves 8-17, basal; petiole subterete, 4.5-8 cm long, 4-6 mm wide; leaf blade elliptic, to broadly ovate, (6.5-9.5) cm × (4.5-6.5) cm, apex obtuse to round, base slightly oblique, cuneate, margin entire, rarely repand, puberulent on both sides, lateral veins 3-5 on each side, prominent abaxially. Cymes axillary, 4-6, 1-4-branched, 3-8-flowered per cyme, peduncle8.0-16.5 cm long, 2-3 mm in diam., with erectly white glandular pubescent; bracts opposite, pale green, linear or linear-lanceolate, ca.8.0 mm × 1.8 mm, pubescent outside, glabrous inside, margin entire to sparsely dentate; bracteoles 2, opposite, the shape, indumentum characteristics and color same as bracts but obviously smaller, ca.4.0 mm × 0.8 mm; pedicel1.1-3.5 cm long, densely pubescent, 0.9-1.2 mm in diam. Calyx 5-parted nearly to the base, lobes linear-lanceolate, (4.0-5.0) mm × (0.8-1.0) mm, pale green, apex acuminate, sparsely white pubescent outside, inside nearly glabrous, margins entire. Corolla pinkish purple, with 8-10 longitudinal dark purple stripes from the throat to the bottom of the corolla tube, 16-20 mm long, externally glandular pubescent, internally sparsely puberulent; tube tubular, ventrally carinate, purplish purple to pink, 10-11 mm long, ca.6 mm in diam. at the base, 8-10 mm in diameter in medium. Limb distinctly 2-lipped, purplish adaxial lip 2-parted to the middle, lobes oblong, ca.6 mm × 3 mm, three purplish vertical lines on each corolla lip; abaxial lip 3-parted to over the middle, lobes broadly oblong, ca.9 mm × 4 mm, rounded at apex. Stamens 2, adnate to ca.6 mm above the corolla tube base, filaments linear, white to translucent, ca.6.5 mm long, geniculate over middle, glabrous; anthers elliptic to reniform, connate at adaxial surface, dorsifixed, ca.2 mm long, glabrous. Staminodes 3, translucent, ca.1 mm long, glabrous, slightly swollen at apex, adnate to ca.6 mm above the corolla tube base. Disk ringlike, ca. 0.8 mm high, margin repand. Pistil11-15 mm long, linear, densely puberulent, ovary yellowish brown, 6-8 mm long, ca.1 mm in diameter, style densely puberulent, white to translucent, 6-8 mm long, nearly glabrous; stigma obtrapeziform, ca.1 mm long, apex 2-lobed. Capsule linear, outside pubescent, 18-24 mm long, ca.2.5 mm in diam., valvate dehiscence when mature.

2 Distribution and Habitat

Up to date, the new species has been only found in Pingguo City, Guangxi, on the surface of wet crevices of rocks surrounding a big karst cave, elevation 220 m, 107°29′ E, 23°16′ N. It grows on the shady surface of limestone rocks. The main associated species are Adiantum flabellulatum L., Alchornea trewioides (Benth.) Müll. Arg., Arachniodes chinensis (Rosenst.) Ching, Asplenium sampsoni Hance, Selaginella moellendorffii Hieron and so on.

2.1 Phenology

Flowering occurs from July to August, and fruiting occurs from August to September.

2.2 Etymology

The specific epithet ‘pingguoensis’ refers to the type locality of this new species.

2.3 Conservation status

Primulina pingguoensis is currently known only from the type locality. The total population size of this new species is small. The mature individuals of the new species are187. Besides, there is a continuing decline in quality of habitat slightly prominent as local villagers have developed animal husbandry in the karst cave and used P. pingguoensis as traditional Chinese medicine by local inhabitant according to our observations and interviews. The extent of occurrence (EOO) is 4 km² and the area of occupancy (AOO) is 0.64 km². Thus, based on currently available information, we propose that P. pingguoensis should be considered as ‘Critically Endangered’ [ (CR) : B1+ B2a], C2b, according to the Guidelines for Using (IUCN) Red List Categories and Criteria (IUCN, 2022) . This species is confronted with habitat destruction and wild extraction, therefore, it is necessary to carry out conservation actions, such as: ex situ conservation and field return, etc.

2.4 Similar species

This new species is morphologically similar to Primulina carinata Y. G. Wei, F. Wen &H. Z. Lü in floral characteristics, but the two species show several diagnostic differences (Table1) . By comparing the new species with other spicies in Prumulina not only P. carinata, we have found that there are other species with carianate corolla more or less, eg, P. dryas, P. polycephala, P. langshanica, and P. roseo-alba, etc. The tube is transitional from funnelform to tubular, all these transitional characters are relation to pollination biology through experimental observation in greenhouse as well as in wild.

Acknowledgements We thank Miss. WEN Zunrong for the handsome drawing.

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