Begonia shenzhenensis, a new species of Begoniaceae from Guangdong, China

Abstract Begonia shenzhenensis D.K.Tian & X.Yun Wang, sp. nov., a new species in Begonia sect. Platycentrum of Begoniaceae from Shenzhen of Guangdong province, China, is described and illustrated. Morphologically, it is primarily similar to B. coelocentroides in the same section but differs by its denser hairs on leaf, petiole, and pedicel, abtuse anther apex, hairy ovary, and narrower adaxial fruit wing. Based on only one small population found to date, its conservation status is assigned to Critical Endangered according to the IUCN Red List Categories and Criteria.


Introduction
Guangdong province is located in southern China, and it borders Macau and Hong Kong, two Chinese special administrative regions. Numerous surveys on plant diversity of this province have been widely conducted by a number of botanists, mainly from several research institutions, including South China Botanical Garden of Chinese Academy of Sciences, Sun Yat-sen University, Guangdong Academy of Forestry, South China Agricultural University, and others. Nonetheless, some new species and new records have been recently discovered Zhou et al. 2020), including two begonia species (Ding et al. 2018;Tu et al. 2020 Diagnosis. The new species is most similar to B. coelocentroides Y.M.Shui & Z.D.Wei in the same section, Begonia Section Platycentrum (J.F.Klotzseh) A.DC. with rhizomatous habit, four tepals of staminate flowers, five tepals of pistillate flower and two-localed ovary, but clearly differs by its densely (vs. sparsely) hairy petioles and blades, hairy (vs. glabrous) ovaries, abtuse (vs. concave) anther apex, and narrower (vs. wider) adaxial fruit wing. It is also close to the small-sized individuals (before mature) of B. edulis in appearance but differs by its short and small (vs. tall and large) and non-stemmed (vs. stemmed) plants, and hairy (vs. glabrous) pedicels, flowers, and fruits (Table 1, Fig. 2).
Etymology. The specific epithet refers to the name of Shenzhen, which includes the type locality of the new species.
Distribution and habitat. The new species is only known from its type locality in Tiantou Mountain Natural Reserve of Pingshan District of Shenzhen, Guangdong Province, China (Fig. 3). It grows together mainly with mosses, ferns, and other herbs on shallow humus soil above the rocks along a small stream under forest canopy.
Conservation status. Begonia shenzhenensis is only observed in its type locality with a very small population containing fewer than 50 individuals. Due to the plant's relatively low ornamental value, it is possibly unlikely to be collected by plant hunters. However, there are no suitable places nearby for spreading its population. Therefore, this species should be considered as Critical Endangered (CE) according to the IUCN Red List Categories and Criteria (IUCN 2019) based on the current data.
Note. The new species was first disovered by Mr. Xiao-Yun Wang, a plant enthusiast working at Hechang Weilai Science and Technology (Shenzhen) Co. Ltd. in Guangdong province of China. On 21 September 2019, Xiao-Yun Wang posted photos of a wild begonia from Shenzhen of Guangdong province, China. At the request of Dr. Dai-Ke Tian, the living plants were collected and introduced to Shanghai Chenshan Botanical Garden for further study. The introduced plants grow well in two plastic pots placed in a squared polymethyl box at 25 °C room temperature and bloom from November to June. On 6 June of 2020, with the help of Xiao-Yun Wang, Dr. Dai-Ke Tian and Dr. Bin Chen conducted a field survey on this species and further confirmed that it is new to science.