Begonia datii (sect. Coelocentrum Begoniaceae) a new species from Quang Binh Province, Central Vietnam Author Hoang, Thanh Son 0000-0003-0351-929X Silviculture Research Institute (SRI) - Vietnamese Academy of Forest Sciences, 46 Duc Thang, Bac Tu Liem, Ha Noi 100000, Vietnam Herbarium of Taiwan Forestry Research Institute, Taiwan Forestry Research Institute, No. 53, Nan-Hai Road, Taipei 100, Taiwan & hoangsonfsiv @ gmail. com; https: // orcid. org / 0000 - 0003 - 0351 - 929 X hoangsonfsiv@gmail.com Author Lin, Che-Wei 0000-0002-8564-5793 varalba @ gmail. com; https: // orcid. org / 0000 - 0002 - 8564 - 5793 varalba@gmail.com text Phytotaxa 2023 2023-08-29 609 4 282 288 http://dx.doi.org/10.11646/phytotaxa.609.4.4 journal article 264461 10.11646/phytotaxa.609.4.4 0795a680-d29e-476e-b22d-ab08745c201f 1179-3163 8297126 Begonia datii T.S.Hoang & C.W.Lin , sp. nov. § Coelocentrum ( Figs.1 , 2 , 3 & 4 A –A’’’) Type: — VIETNAM . Quang Binh Province , Minh Hoa district , Thuong Hoa commune, 495 m elev., grows on limestone mountains under secondary forests, 20 April 2022 , Hoang Son 4435 ( holotype VAFS , isotype VNMN ) . FIGURE 1. Distribution map of Begonia datii (red star), B. bamaensis (orange hexagon), B. filiformis (blue circles), B. longistyla (pink diamond), B. montaniformis (yellow square), B. morsei Irmsch (green triangle) and B. morsei var. myriotricha Y.M.Shui & W.H.Chen (purple inverted triangle) in China and Vietnam. Diagnosis: —It resembles B. filiformis in its habit, leaf shape and texture, but it can be easily distinguished from the latter by its peduncle and inflorescence covered with villous hairs (vs. glandular-hispid), bracts caducous (vs. persistent or semi-persistent), tepals pinkish-white to pink (vs. yellowish-green), glabrous outer tepals of pistillate flowers (vs. glandular-hispid abaxially), ovary and wings glabrous (vs. glandular-hispid). Monoecious rhizomatous herb. Rhizome stout, crimson to reddish-brown, 8–20 mm thick, internodes congested, villous. Stipules persistent, yellowish-red to reddish-brown, narrowly triangular, 6–14 × 3.5–8 mm , herbaceous, strongly keeled, midrib sparsely hirsute, margin entire, apex aristate, arista 2.5–5 mm long. Leaves alternate, petiole terete, maroon to red, 9–31 cm long, 4–10 mm diameter, densely white villous; leaf blade asymmetric, thick chartaceous, succulent, widely ovate, 13–22.5 × 8.5–16 cm , broad side 5.3–10 cm wide, basal lobes cordate, 3.8–6.7 cm long, margin denticulate with a line of pinkish-white puberulous hairs, apex acuminate to caudate; adaxial surface emerald green, dark olive green to blackish-green, embellished with silvery white patches or semicontinuous stripes of variable sizes between major veins, rarely completely green, densely covered by small raised cones each topped by a pinkish-white to magenta puberulous hairs, giving a wrinkled texture; abaxially purplish-red to magenta; venation basally ca . 7 palmate, midrib distinct, ca . 2 secondary veins on each side, other primary veins branching dichotomously or nearly so, tertiary veins reticulate; major veins densely pinkish-white to magenta puberulous on adaxial surface, densely pink to magenta puberulous on all veins abaxilly. Inflorescences axillary, bisexual, cymose panicle arising directly from rhizome, ca . 4 orders of branching; peduncle red, 13.2–25.5 cm long, villous. Bracts caducous, yellowish-red, at basal node of inflorescence ovate, 10–17 × 7–10 mm , abaxially villous or glabrous, margin with a line of villous; bracts on upper nodes similar but gradually smaller. Staminate flower: pedicel pinkish-yellow to rosy pink, 1–3.5 cm long, villous or glabrous, tepals 4, pinkish-white to pink, outer 2 ovate to widely ovate, 8–15 × 10–13 mm , abaxially glabrous or villous, margin entire, apex rounded to obtuse, inner 2 narrowly obovate, 7–10 × 3–4.5 mm , glabrous, apex obtuse or rounded; androecium nearly actinomorphic, ca . 5 mm across; stamens golden yellow, 65–100; filaments ca. 1.5 mm long, fused at base; anthers obovate, ca . 1 mm long, 2-locular, apex truncate to slightly retuse. Pistillate flower: pedicel pinkish-yellow to rosy pink, 12–23 mm long, glabrous or very sparsely villous, tepals 3, pink, glabrous; outer 2 suborbicular, 8–12 mm across, margin entire, apex rounded, inner 1 oblanceolate to narrowly elliptic, ca . 5 × 3 mm , apex obtuse; ovary trigonous-ellipsoid, 7–10 mm long, ca . 4 mm thick (wings excluded), rosy pink to pinkish-yellow, glabrous; 3-winged, wings unequal, rosy pink to yellowish-pink, glabrous, margin entire; wings crescent-shaped, 9–12 mm long, lateral wings narrower, 2–4.5 mm wide, abaxial wing 3–6.5 mm wide; ovary 1-locular with intruded parietal placentation, placentae 3, bilamellate; styles 3, fused at base, golden yellow, ca. 3.5 mm long, stigma spirally twisted. Capsule capsule trigonous-ellipsoid, 13–18 mm long, 5–7 mm thick (wings excluded), reddish-green when fresh; wings unequal, 15–20 mm long, lateral wings 5–7 mm wide, abaxial wing crescent-shaped to sub-triangular, 7–13 mm wide, cuneate at the base, rounded to truncate at the apex. FIGURE 2. Begonia datii T.S.Hoang & C.W.Lin. A. Habit ; B, B’. Portion of leaf adaxial and abaxial surfaces; C. Stipule; D–D’’’. Bracts; E, E’. Staminate flower, face and side views; F, F’. Stamens, dorsal and ventral views; G, G’. Pistillate flower, face and side views; H, H’. Style and stigmatic band, dorsal and ventral views; I, I’. Capsules; J. Cross section of ovary. FIGURE 3. Begonia datii T.S.Hoang & C.W.Lin. A , B, C. Habit and habitats; D. Rhizome and petioles; E. Stipules; F. Portion of leaf adaxial surface, G. same, abaxial surfaces; H. Inflorescence, also showing bracts; I. Staminate flowers, face and back views; J. Pistillate flowers, face and side views; K. Capsule; L. Cross section of ovary. All from Hoang Son 4435 by T.S. Hoang. FIGURE 4. Morphological comparison of Begonia datii and allied taxa, showing habits and morphological characters: B. datii (A–A’’’), B. bamaensis (B–B’’’), B. filiformis (C–C’’’), B. longistyla (D–D’’’), B. scabrifolia (E–E’’’). A, B, C, D, E. Habit; A’, B’, C’, D’, E’. Leaf, adaxial surfaces; A’’, B’’, C’’, D’’, E’’. Portion of leaf adaxial surfaces; A’’’, B’’’, C’’’, D’’’, E’’’. Flowers. A–A’’’ from Hoang Son 4435 and C–C’’’ from Hoang Son 6433 by T.S. Hoang; B–B’’’ from Peng 18752 , D–D’’’ from Peng 20435 and E–E’’’ from Peng 22197 by C.-I Peng. Distribution and ecology: —Currently only known from the type locality in Thuong Hoa commune. The Thuong Hoa commune borders the Nakai-Nam Theun National Park in Laos , therefore, it is possible that this species occurs there also. The species grows on limestone mountains under secondary forests at 495–510 meters above sea level. Etymology: —The epithet is in honor of Mr. Bui Tien Dat, who is the first to discover this new species. Conservation: —There were only four populations found at the site of collection with a total of less than 200 mature individuals recorded, while the nearby habitats are remote and virtually uninhabited. For the reason that the populations have restricted distribution, it may be considered as Near Threatened species, according to the IUCN 2022. Notes: —Within Begonia sect. Coelocentrum , the number of described species has increased by more than 20 in the last decade, mostly from disoveries concentrated in southwestern China and northern Vietnam . There are now 22 species in the section known from Vietnam , however, only two of these occur in the central region of the country: B. montaniformis ( Peng et al. , 2015 ) ( Fig. 1 ) and B. cavaleriei ( Léveillé, 1909 ) . The newly discovered Begonia datii from Quang Binh Province is the third record of the section from Central Vietnam . Although Central Vietnam is at the edge of the range of the section, the low number of species in the area could also be an artifact of it being botanically poorly explored. Morphologically, B. datii is most similar to B. filiformis ( Irmscher, 1939 ) ( Fig. 4 C –C’’’) from southwestern China to northern Vietnam ( Fig. 1 ) in its robust rhizome with congested internodes, widely ovate leaves that are rugose and variegated; a detailed comparison of characters is presented in Table 1 . Moreover, B. bamaensis ( Liu et al. , 2007 ) ( Fig. 4 B –B’’’), B. longistyla ( Shui & Chen, 2005 ) ( Fig. 4 D –D’’’), B. morsei var. morsei ( Irmscher, 1939 ) , B. morsei var. myriotricha ( Shui & Chen, 2005 ) and B. scabrifolia ( Liu et al. , 2020 ) ( Fig. 4 E –E’’’) are similar in maculation and having rugose leaves, however, B. datii can be distinguished from these five species by a combination of morphological characters ( Table 1 ), and the geographic distributions of those taxa are distant ( Fig. 1 ).