Seven new species and seven new records of Begonia L. (Begoniaceae) in the flora of Laos

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This paper provides results of critical studies of herbaria presently available at the National Herbarium of Laos (HNL), National University of Laos (FOF), Biology Herbarium of the National University of Lao PDR (NUoL), Forest Research Central Herbarium of the National Agriculture and Forest Research Institute (FRC), as well as living plants and alcohol preserved material at Pha Tad Ke Botanical Garden. Additionally, relevant literature available online at the Begonia Resource (Hughes et al., 2015-) and Biodiversity Library website (https:// www.biodiversitylibrary.org/) was studied, along with specimen images available online at BM, E, K, LE, NY, P, and PE Herbaria. Keys and descriptions provided by Doorenbos et al. (1998) and Moonlight et al. (2018) were used for the identification of the genus sections. Completed investigation reveals seven new species for science and seven species newly recorded for the flora of Lao PDR. These discoveries are results of botanical surveys of Hin Nam No National Protected Area, Nam Phouy National Protected Area, Khammouane karst forest, and Phou Khao Khouay National Protected Area. Descriptions and line drawings are provided for all newly described species. Photographic illustrations, data on phenology, habitat, and notes on morphological variations and relations are given for all studied species.  (Fig. 1, 2A).
Distribution. This species is endemic to Hin Nam No National Protected Area (Khammouane Province, Boualapha District).
Ecology and phenology. Wet rock crevices in humid places of limestone deciduous forest. Flowers from August to October, fruits in October. Vernacular name. Som Saeng Pha (hill begonia).  Notes. The new species belongs to B. sect. Reichenheimia, which includes 22 species in SE Asia, including our new species. All species of the section are tuberiferous plants having flowers with 3 stigmas, 3-locular ovary, and placental branches   (VU B1,2ab (i,ii,v)). Begonia glabritepala is known only from the type locality within Hin Nam No Protected Area. The known species area of occupancy is 4 km 2 and extent of occupancy is 820 km 2 . The individuals form less than 5 colonies. Hence, we consider B. glabritepala to be Vulnerable under the VU B1 and 2 criteria.  (Hong-Bo et al., 2020b). From mentioned species, it differs in reddish purple, glandular pubescent abaxial leaf surface (vs. abaxial surface light green, densely white villous), glandular pubescent pedicel (vs. pedicel puberulous), and outer tepals of pistillate flowers sparsely white glandular pubescent (vs. tepals almost glabrous, light pinkish) (Fig. 2B, 3).
Ecology and phenology. Wet sandy soil in deciduous forest mixed with bamboo. Flowers in September, fruits in October. Vernacular name. Som Koung Khao Dang (white speckled begonia).
Notes. The characteristic arrangement of leaves and glandular hairy ovary of this species are similar to B. namkadingensis C.-J. Yang, Souladeth et Tagane and B. pteridiformis Phutthai from B. sect. Lauchea (Moonlight et al., 2018). Meanwhile, our plant differs in having 3-lobed ovary with one branch per locule (vs. 2-lobed ovary with two branches per locule). The specific epithet refers to dorsal wing of capsule that looks like broad spine.
Proposed IUCN (2019) category. Endangered (EN B1, 2bc (i, ii, iv). Begonia heterocantha is very rare plant currently known only from the type locality with less than 15 observed plants. The known area of the species occupancy covers less than 4 km 2 and extent of occupancy not more than 2 km 2 . Hence, we consider B. heterocantha as an endangered species under the IUCN criteria EN B1 and 2. Diagnosis. This species is closest to B. paleacea Kurz in having inflorescences arising from the base of the leaves, but it differs in having elongate tubers (vs. tubers globose), ovate-lanceolate, obscurely asymmetrical to symmetrical leaves (vs. leaves distinctly asymmetrical, ovate to orbiculate), and glabrous pedicels (vs. pedicels glandular pubescent) (Fig. 2C, 4).
Distribution. Known only from type locality at Phou Khao Khouay National Protected Area (Vientiane Province).
Ecology and phenology. Moist mossy rocks in seasonally dry evergreen forest mixed with bamboo on the hill slopes. Flowers in May -June.
Notes. This species is similar to B. poilanei Kiew (B. sect. Diploclinium) in elongate tubers and dark color patches along veins on the adaxial leaf surface. The leaves of B. lanxangensis are narrowly ovate, inflorescences arise from the base of the leaf, two stigmas, ovaries with two locules; in the opposition, B. poilanei has broadly ovate leaves, inflorescences arising from the tuber, three stigmas, and ovaries with three locules (Kiew, 2007). The species epithet refers the old name of Lao PDR, which means "Kingdom of million elephants", as well as Phou Khao Khouay National Protected Area is one of a few elephant habitats still existing in the country.
Proposed IUCN (2019) category. Begonia lanxangensis is currently only known from the type locality situated in Phou Khao Khouay National Protect Area. Local people use the area of species location for recreation and pasturing that seriously disturbs the alone known population. Thus, the species is estimated as becoming Critically Endangered in the near further. Hence, we consider a category of VU D2 to be appropriate for this species. Diagnosis. The plant is most similar to B. martabanica A. DC. but differs in smaller habitus, reniform-cordate leaves (vs. leaves ovate), peduncle, pedicle and capsules with glandular hairs (vs. pubescent with simple hairs) (Fig. 2D, 5).

Distribution. Endemic of Phou Khao Khouay National Protected Area (Vientiane Province).
Ecology and phenology. Moist mossy rocks in seasonally dry evergreen forest mixed with bamboo near stream. Flowers in July -October, fruits in October -November.
Proposed IUCN (2019) category. Endangered (EN B1ab(i, ii, v)). Begonia parviglandulosa is currently known from the only type locality at Tad Xang Waterfall in Phou Khao Khouay National Protected Area. This area is affected by intensive recreation by tourism and local people harvesting a lot of medicinal and edible plants, as well as firewood that seriously disturbs primary habitats. The known area of this species occupancy is ca. 4 km 2 . All observed individuals form less than 50 colonies. Hence, we consider B. parviglandulosa to be endangered species under the EN B1 IUCN criterion.
Additional specimens examined. The same location as holotype, 22 July 2018, Lanorsavanh S., Lamxay C., SL 1457 (KKU, QBG and alcohol preserved collection at Biology herbarium of National University of Lao PDR). Diagnosis. The new species is similar to B. brandisiana Kurz but differs in pistillate flowers having five tepals (vs. pistillate flowers with two tepals), outer pairs of tepals of both staminate and pistillate flowers elliptic-oblanceolate (vs. tepals orbiculate) (Fig. 2E, 6).
Distribution. This species known only from Tham Nang Ene Cave Preserved Area (Khammouane Province, Thakheak District).
Ecology and phenology. Rock on limestone hills covered by deciduous forest in association with Globba sp., Zingiber sp., Impatiens sp., and Argostemma sp. Flowers in June -August, fruits in July -September. Vernacular name. Som Koung Bai Dok Thong (butea leaf begonia).
Notes. This species is also similar to B. demissa Craib in having the same number of tepals in staminate and pistillate flowers but differs in lack of whorl of leaves at the base of inflorescence (vs. two-four leaved whorl at the base of inflorescences), and in reniform to semi-orbiculate leaves (vs. leaves triangular cordate). The specific epithet refers to the superficial similarity of the new species with B. brandisiana.
Proposed IUCN (2019) category. Vulnerable (VU D2). The lone known population of B. pseudobrandisiana at Tham Nang Ene tourism area includes less than 30 individual plants. The species area of occupancy is about 4 km 2 , and the extent of occupancy is less than 20 km 2 . The collecting of samples by numerous tourists as an Diagnosis. The species is similar to B. tricuspidata C. B. Clarke from B. sect. Alicida C. B. Clarke but differs in having leaves palmate triangular-ovate, with deeply lobed lacerate margin (vs. leaves ovate with almost entire or crenate margin), pistillate flower with five tepals (vs. pistillate flowers with four tepals), ovary with unequal wings, dorsal wing smaller, triangular, lateral wings broadly lunate (vs. ovary with subequal wings) (Fig. 2F, 7).
Ecology and phenology. Limestone rocks on wet slopes in open forest or scrub in association with Microchirita sp., Argostemma sp., and Adiantum sp. Vernacular name. Som Koung Bai Seak (deeply lobe-leaved begonia).
Notes. In its habitus, new species is similar to B. demissa Craib from B. sect. Diploclinium but differs in palmate triangular, deeply lobed, lacerate leaves, (vs. leaves triangular with biserrate margin), and triangular dorsal wing of ovary (vs. dorsal ovary wing cucullate). The specific epithet means deeply lobed, mainly tripartite leaves.
Proposed IUCN (2019) category. Endangered (EN B2). Begonia tripartifolia is known only from the type locality in Khammoune Province. The known species area of occupancy is 4 km 2 , and the extent of occupancy is 820 km 2 . Mining and cement factory activity in this area are the main factors of habitat lost. Hence, we consider B. tripartifolia to be endangered species under the EN B2 IUCN criterion.
Diagnosis. This new species is similar to B. sinuata Wall. ex Meisn. but differs in single leaf, indumentum of bristle hairs and reddish or bronzy green adaxial leaf surface (vs. two-three leaves, indumentum of stellate hairs and dark green adaxial surface of leaf), three styles (vs. two styles), and glandular hairy pedicels (vs. pedicels with stellate hairs) (Fig. 8, 9A).
Ecology and phenology. Wet limestone and granite rock in association with Asplenium sp., Adiantum sp., Globba sp., and Zingiber sp. Flowers in June -August, fruits in September -October. Vernacular name. Som Koung Tham (cave begonia).
Notes. The new species resembles B. poilanei from Vietnam in solitary leaf and elongate tubers but