Five new species of the genus Primulina (Gesneriaceae) from Limestone Areas of Guangxi Zhuangzu Autonomous Region, China

Abstract Five new species of Primulina (Gesneriaceae) are described and illustrated here, namely P.purpureokylin F. Wen, Yi Huang & W. Chuen Chou, P.persica F. Wen, Yi Huang & W. Chuen Chou, P.cerina F. Wen, Yi Huang & W. Chuen Chou, P.niveolanosa F. Wen, S. Li & W. Chuen Chou and P.leiyyi F. Wen, Z.B. Xin & W. Chuen Chou. The characteristic traits of these species, together with photographs, detailed descriptions, notes on etymology, distribution, and habitat, as well as comparisons with morphologically similar species, are provided.


Introduction
The genus Primulina sensu lato, as a group, is representative of the rich diversity of Chinese Gesneriaceae. The tropical and subtropical karst limestone mountainous areas of Guangxi, China, are the centers of species diversity and differentiation of this genus. As of the end of June 2017, the accepted and published species of Primulina from China had already reached 180 (includinginfraspecific taxa). Among them, 115 species (more than 63%) are confirmed and recorded from Guangxi Zhuangzu Autonomous Region (Guangxi for short)    (Yang et al. 2019). Guangxi is located in southern China. Most of the province originates from erosion of a limestone plateau and has a subtropical monsoon-affected climate. Several new species of Gesneriaceae have been discovered and published in recent years from this region. We suspect that more new taxa of Primulina, and even Gesneriaceae, are still to be found here.
The Guangxi Institute of Botany continues to support the Gesneriad Conservation Center of China (GCCC) and the Guilin Botanical Garden, CAS, in carrying out the investigations of Gesneriaceae diversity in S & SW China in recent years. Since 2015, the GCCC has been introducing, conserving, and propagating a large number of Primulina plants from S and SW China and N Vietnam. Many Primulina species from the Guangxi area are new to science, and waiting to be further studied. After careful study of both relevant specimens and taxonomic publications from the adjacent regions (Wang et al. 1990(Wang et al. , 1998Wang 2005, Wei et al. 2010;Weber et al. 2011;Möller et al. 2016;Xu et al. 2017 (Xu et al. 2010 in having similarly purple indumentum on both surfaces of the leaf blade, but differs in having fewer leaves (4-6 in P. purpureokylin vs 5-12 in P. leprosa; same order as following), smaller leaf blade size (2-6.5 × 1.5-3.5 cm vs. 6-13 × 4-8 cm), bracts shape (linear or linear-lanceolate vs broadly ovate), corolla color (pinkish purple vs. yellow) and length (1.5-1.8 cm long vs. ca. 2.3 cm long), staminodes number (2 vs 3) and indumentum of style (nearly glabrous vs glandular-pubescent).
Phenology. Flowering in Nov., fruiting time in Dec.
Etymology. The specific epithet, 'purpureokylin', consists of two parts. The first part of the scientific epithet is "purpure-", means purple. It refers to the upper faces of the leaf blades which are covered in purple pubescent-hairs. The second half of the epithet, "kylin", refers to one of the auspicious animals in the traditional culture of China. Because the interesting and beautiful leaves are full of purple-hairs, bubbles on the surface appear as if covered with the purple squamae of Kylin. The Chinese name is "Zí Líng Bào Chūn Jù Tái" (紫麟报春苣苔).
Distribution and habitat. Primulina purpureokylin is currently known only from the type locality. Only a single population with ca. 100 individuals was discovered and confirmed. The species is only known growing on the surface and crevices of wet limestone rocks at the bottom of cliffs in Pingguo County, Guangxi, China.
Provisional IUCN conservation assessment. Along with the further field investigations for the current survival situation of Primulina purpureokylin, the extinction risk of this species is rising because of over-harvesting by local plant collectors. Overexploited because of its beauty, this unpublished species is on the brink of extinction. Although more surveys are needed to clarify its conservation status, the provisional conservation status is Critically Endangered CR B2ab (iii, v) according to the IUCN red list criteria (IUCN 2012).  (Huang et al. 2012) in having similarly shaped leaf blades. It differs from the latter by having a different indumentum on both surfaces of the leaf blades (densely eglandular-pubescent in P. persica vs densely glandular-pubescent in P. gongchengensis; same order as following), margin of leaf blade (irregularly serrate in different numbers vs. repand or crenate), smaller bracts (6-7 × 1.5-2 mm vs. 10-20 × 2-3.5 mm) and bracts shape (linear vs. narrowly rhombic to oblong), the indumentum of calyx lobes inside (glabrous vs sparsely glandular-pubescent) and shorter corolla length (7.5-10 mm long vs. 22-28 mm long).

Phenology.
Flowering from May to June; fruiting from June to August. Etymology. The specific epithet, 'persica', refers to the color of its flower, a vivid and bright peach. The Chinese name is "Tāo Hóng Xiáo Huā Jù Tái" (桃红小花苣苔).
Distribution and habitat. Primulina persica is currently known only from the type locality and only about 50 individuals were confirmed. All individuals are growing on the surface of tufa and wet crevices of moist rocks on the cliff of a limestone hill in Yangshuo, Guangxi, China. There are no accompanying plants except for some ferns.
Provisional IUCN conservation assessment. The original habitat of this species was almost destroyed because of road building in 2013; it directly resulted in a single small population with no more than 50 surviving individuals. We hope we can find more populations in the future through field surveys. The habitat of Primulina persica is likely to be subjected to human activities because the survival population grows in cracks of a limestone cliff by the side of the road. Thus, based on currently available information, P. persica should be considered as 'Critically Endangered' (CR): B1+2ab(V); C2b, following the IUCN categories and criteria (IUCN 2012).  (Fig. 6 C) (Fang and Qin 2004, Wang et al. 2011, Weber et al. 2011 in having similarly shaped leaf blades, but differs in their indumentum of the peduncle (densely erectly eglandular-puberulent in P. cerina vs spreading white pubescent and glandular puberulent in P. renifolia; same order as following), corolla tube shape (tubular, abaxially straight and not swollen vs. obliquely campanulate, abaxially swollen), corolla color (beige to pale yellow mixed slightly reddish brown vs. pale purple to purple inside longitudinally purple lines), indumentum of filaments (glabrous vs glabrous but base glandular puberulent), the indumentum of calyx lobes inside (glabrous vs sparsely glandular-pubescent) and stigma shape (obtrapeziform and 2-lobed vs obliquely hippocrepiform but unlobed).
Phenology. Flowering from April to May; fruiting from June to July. Etymology. The specific epithet, 'cerina', refers to the special color of the flowers; 'cerina' is derived from the Latin, 'cerinus', meaning dark yellow or sulfur yellow, but mixed with a little pale reddish brown. The color seems like the hue of the natural brimstone (sulphur) ore. The Chinese name is "Àn Líu Sè Xiáo Huā Jù Tái" (暗硫色小花苣苔).
Distribution and habitat. Primulina cerina is currently known only from the type locality. The species grows in the crevices of rocks with wet surfaces at the entrances of a large limestone cave in Yizhou, Guangxi, China.
Provisional IUCN conservation assessment. Primulina cerina is rarer than the species mentioned above, P. persica. At present, only a single population with ca. 20 individuals is known, counted and confirmed from 2016 to 2018. Although the type locality is in an outlying mountain area and surrounded by limestone forest, this species should be assessed as 'Critically Endangered, CR B2a+C2a(i,ii)+D', given the few known individuals and a single population based on the IUCN categories and criteria (IUCN 2012). Diagnosis. Primulina niveolanosa most closely resembles P. repanda (W.T. Wang) Y.Z. Wang (Fig. 6 D) (Wang 1981, Wang et al. 2011, Weber et al. 2011 in having similarly shaped leaf blades, but differs in their indumentum of the leaf blades (both surfaces spreading densely long white villous to lanate in P. niveolanosa vs. appressed puberulent to villous in P. repanda; same order as following), number of bracts (3, whorled vs. 2, opposite), shape of bracts (narrowly oblong to broadly oblanceolate vs. lanceolatelinear to subulate), shape of calyx lobes (linear to narrowly oblanceolate vs. narrowly triangular), corolla length (1.5-1.8 cm long vs. ca. 8 mm long).
Phenology. Flowering from March to April; fruiting from April to May. Etymology. The specific epithet, 'niveolanosa', consists of two parts. The first part of "niveo", comes from the Latin word, 'niveus', and means as white as snow, or snowwhite; the second half, 'lanosa', is from the Latin, 'lanosus, lani-', meaning with lanose or villous hairs. Thus, the scientific name refers to the plants seemingly covered with snow because of the indumentum of snowy lanose hairs. The Chinese name is "Mián Máo Xiáo Huā Jù Tái" (绵毛小花苣苔).

Primulina leiyyi
Phenology. Flowering from November to the beginning of December; fruiting in January of the next year.
Etymology. The new species is named after Mr. Yu-Yang Lei, who first discovered and collected this rare species and who accompanied us on a number of subsequent field expeditions in Nanning, Guangxi. The Chinese name is "Léi Shì Bào Chūn Jù Tái" (雷氏报春苣苔).  A P. leprosa, the congener of P. purpureokylin B P. gongchengensis, the congener of P. persica C P. renifolia, the congener of P. cerina D P. repanda, the congener of P. niveolanosa E P. longgangensis, the congener of P. leiyyi. Photographed by Fang Wen, charted by Wen-Hua Xu. Distribution and habitat. It is currently known only from the type locality in a single population with ca. 100 individuals. Although it might be endangered, more surveys are needed to clarify its conservation status. The species is only known growing on the surface of wet rocks on the limestone hills along the edges of village roads.
Provisional IUCN conservation assessment. We carefully explored the type locality on five visits over a period of three years. Primulina leiyyi appears to be restricted to limestone hills surrounding Shibaluohandong village, Suxu Town, Nanning city. Although the habitats are very near to densely populated areas and are easily threatened by human activities, this species is common and locally abundant on limestone hills. Using the IUCN Red List categories (IUCN 2012), a provisional conservation status of Least Concern (LC), is assessed for this species.