﻿Vacciniumbangliangense, a new species of Ericaceae from limestone areas in Guangxi, China

﻿Abstract Vacciniumbangliangense, a new species from limestone areas in Guangxi, China, is described and illustrated. It is morphologically most similar to V.pseudotonkinense and V.sciaphilum in having small and dense obovate leaf blades with a retuse apex, hairy young branches and calyx and campanulate corollas, but can be distinguished from them by the distance of basal gland from petiole, the length of peduncle, pedicle and filaments, the indumentum of calyx tube and corolla and the existence of apical glands on calyx lobes. A table to distinguish the new species from other morphologically similar Vaccinium species, as well as colour plates of comparison of key characters, is also provided.


Introduction
Xia 2015; Tong et al. 2018Tong et al. , 2020Tong et al. , 2021aTong et al. , b, 2022. As one of the most biodiverse regions of China, Guangxi has 27 species and two varieties of the genus Vaccinium, including four endemic species, viz. V. damingshanense Y.H. Tong & N.H. Xia, V. napoense Y.H. Tong & N.H. Xia, V. crassivenium Sleumer and V. cuspidifolium C.Y. Wu & R.C. Fang (Qin and Liu 2010;Tang 2011;Huang et al. 2015;Tong and Xia 2015;Tong et al. 2018Tong et al. , 2020. During fieldwork in Bangliang Gibbon National Nature Reserve of Guangxi in June 2021, we discovered a special flowering plant of Vaccinium never recorded from Guangxi with the characteristics of inflorescence being shortly racemose, axillary or borne on leafless old stems, peduncle being very short or 4-5 mm long and corolla being broadly campanulate, yellowish-green or tinged reddish. After consulting Flora of China (Fang and Stevens 2005) and other relevant literature (Dop 1930;Pham 1999;Nguyen 2005;Newman et al. 2007;Qin and Liu 2010;Tang 2011;Tong and Xia 2015;Watthana 2015;Tong et al. 2020), as well as comparisons amongst this unknown species and its morphologically most similar species, based on herbarium specimens including types, we confirmed that this species is new to science, which is described and illustrated below.

Materials and methods
Field surveys have been conducted in flowering and fruiting phases at the type locality. Measurements and assessments of morphological characters were based on the living plants in the wild and the specimens gathered from the type locality. Type specimens were deposited in the herbaria of South China Botanical Garden (IBSC) and Guangxi Institute of Botany (IBK). The comparisons amongst this unknown species, V. sciaphilum C.Y. Wu and V. pseudotonkinense Sleumer were based on the descriptions from protologues and the examination of herbarium specimens or photos of specimens (including types) at IBK, IBSC, KUN and P (Sleumer 1941;Fang and Wu 1987 Sleumer (1941) and is morphologically similar to V. pseudotonkinense Sleumer and V. sciaphilum C.Y. Wu in having small and dense obovate leaf blades with a retuse apex, hairy young branches and calyx and campanulate corollas, but can be distinguished from the former by basal glands on leaf blade margin at 0.3-0.8 mm (vs. 2.6-4 mm, Fig. 3C) distance from petiole, inflorescence with very short peduncle or up to 5 mm long (vs. very short, Fig. 2E), calyx lobes with ciliolate margin and a gland at apex (vs. with ciliate and glandular margin and without a gland at apex, Fig. 3D) and, from the latter, by inflorescence with very short peduncle or up to 5 mm long (vs. very short, Fig. 2G), longer (5-7 mm vs. ca. 3 mm) and glabrous (vs. densely pubescent, Fig. 2G) pedicel, glabrous or sparsely villous (vs. densely hispid) calyx tube, glabrous or sparsely pubescent (vs. densely hispid, Fig. 3F) calyx lobes with a gland at apex (vs. without a gland at apex, Fig. 2I) and densely villous (vs. glabrous) filaments. A detailed morphological comparison amongst the three species is summarised in Table 1.
Etymology. The specific epithet is derived from the type locality, Bangliang Gibbon National Nature Reserve of Guangxi, China. The Chinese name is given as " 邦亮越橘 (pinyin: bāng liàng yuè jú)".
Distribution and habitat. Thus far, Vaccinium bangliangense was found only in Bangliang Gibbon National Nature Reserve of Guangxi, China. It usually grows on rocks of limestone hillside or peak at an elevation from 850-900 m, sometimes on the trunks of Pistacia weinmanniifolia J. Poisson ex Franchet (Anacardiaceae). The slope direction is to the south and the slope gradient is ca. 30°. The tree layer is up to 8 m tall with a canopy cover of 70% and the shrub and herb layer covers are 85% and 20%, respectively. The associated species include Quercus phillyreoides A. Conservation status. Vaccinium bangliangense has only been found in Bangliang Gibbon National Nature Reserve of Guangxi, China. As a new species, more subpopulations of V. bangliangense could probably be found in similar habitats of surrounding limestone areas in the future. However, wild surveys have been conducted for more than ten years in the area where the new species was found. Only two subpopulations were found in the protected region with a total of fifteen individuals and seven of these are mature. Based on the current data, its population size is very small, and the area of occupancy (AOO) is restricted. According to Guidelines for Using the IUCN Red List Categories and Criteria (IUCN Standards and Petitions Committee 2022), the conservation status of V. bangliangense should be assessed as Critically Endangered (CR), based on criteria D of (IUCN 2012).

Discussion
In Guangxi, another species of V. sect. Conchophyllum, namely V. triflorum Rehder, is also somewhat similar to this new species in the small and dense leaves, short racemes and campanulate corollas, but can be readily distinguished by its thickly leathery and elliptic or obovate-elliptic leaf blades with a strongly rugose adaxial surface. The two species also have allopatric distribution in Guangxi: V. triflorum is distributed in Huanjiang County, north Guangxi, while V. bangliangense occurs in Jingxi County, southwest Guangxi.
Two kinds of flower colour of Vaccinium bangliangense were observed in the wild: the plants growing in shaded habitat always bear inflorescences with yellowish-green flowers and longer peduncles (Figs 1F, 2B), while inflorescences with tinged reddish flowers and shorter peduncles (Figs 1E, 2A) are normally found in sunlit habitat. In addition, the leaf blades of plants growing in shady habitat are thinner and with sparsely white villous margin (Fig. 2B), while those of plants growing in sunlit habitat are thicker and with less hairy or glabrous margins ( Fig. 2A). It is speculated that these variations on flower colour, peduncle length and texture and indumentum of leaf blades may be caused by different light intensity.
Vaccinium bangliangense is a small shrub with a beautiful tree form and thus an excellent species for landscaping. It is adaptive to limestone areas and has important application value in limestone mountain greening. The first author once inserted one branch of this species into clear water for more than 3 months and surprisingly found that it grew new roots, which indicates that this plant is relatively easy to be cultivated.