Begonia tadungensis T.V.Do, 2020

Do, Truong Van, Luu, Anh Ngoc Dam & Dong, Wen-Ke, 2020, Begonia tadungensis (Begonia sect. Platycentrum), a new species from southern Vietnam, Phytotaxa 449 (1), pp. 65-74 : 70-71

publication ID	https://doi.org/ 10.11646/phytotaxa.449.1.6
persistent identifier	https://treatment.plazi.org/id/039D1879-1269-FFA7-FF53-71930C2FE198
treatment provided by	Felipe
scientific name	Begonia tadungensis T.V.Do
status	sp. nov.

Treatment

Begonia tadungensis T.V.Do View in CoL , sp. nov. ( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

The new species is most similar to B. albopunctata Chen et al. (2018a: 66) in its broadly ovate leaves; red and 4- loculed ovary with three free styles; 2-lobed stigmas with twisted band; and red, berry-like fruits with a beaked apex, but differs principally in its glabrous abaxial leaf surface (vs. densely red pubescent), 1.8–2 cm long peduncle (vs. 6–9 cm), 2.5–4 cm long pedicels of staminate flower (vs. 0.5–1.5 cm), puberulous outer surface of tepals (vs. almost glabrous), 1.8–2 cm long pedicels of pistillate flower (vs. 0.4–0.7 cm), six tepals of pistillate flower (vs. five), and obovate or turbinate, wingless, and puberulous fruits (vs. rhomboid, four thickened rib-like horns, and densely white papillose).

Type: — VIETNAM. Dak Nong province: Dak Glong district, Dak Som commune, Dak D’Linh stream, Ta Dung National Park , elev. 751 m, 11°48.854’ N, 107°58.977’ E, on the moist rocky along the stream banks in broad-leaved evergreen forests, 23 May 2019, Do Van Truong 346 (Holotype: VNMN; Isotype: HN) GoogleMaps .

Monoecious, perennial herb. Rhizome 5–7 cm long, 0.8–1.1 cm in diam, rooting at nodes; internodes 5–6 mm long, reddish-brown with white dots, glabrous. Stipules broadly triangular or ovate, 1.1–1.5 × 0.6–0.8 cm, pinkish-red, margin entire, apex acuminate, up to 1.3 cm long, outside puberulous, inside glabrous. Leaves alternate, petiole terete, brown to reddish-brown, 12–25 cm long, 2–4 mm in diam., fleshy, covered with grayish hairs; leaf blade asymmetric, oblique, ovate or broadly ovate, 12–26 × 8–20 cm, base cordate, basal lobes 2–2.5 cm deep, apex acute to acuminate, margin slightly denticulate, short ciliate, adaxially dark green, setulose, abaxially grayish-green, subglabrous; venation palmate, reddish, 7–8 primary veins, secondary veins branching dichotomous, tertiary veins obviously reticulate, sparsely puberulous on veins, all venation prominently raised abaxially, adaxially slightly sunken except for primary veins. Inflorescence axillary, twice branched dichasia, 3–10-flowered; peduncle erect, reddish, 1.8–2 cm long, sparsely gray puberulous; rachis 5–6 mm long; bracts pale green, narrowly triangular to lanceolate, 6–7 × 3–4 mm, margin entire, glabrous. Staminate flower: pedicel erect, pink to pinkish-red, 2.5–4 × 0.1 cm, puberulous; tepals 4, white to pinkish-white, puberulous on outer surface and glabrous on inner surface; outer tepals 2, oval to elliptic, 0.9–1 × 0.6–0.8 cm, apex rounded, margin entire; inner tepals 2, smaller, obovate to oblanceolate, narrower than outer tepals, 0.9–1 × 0.4–0.5 cm, margin entire; stamens numerous, filaments free, 0.4–0.5 mm long, anthers yellow, oblanceolate, 1–1.2 mm long, apex rounded, longer than filament, with longitudinal slits. Pistillate flower: pedicels pendulous, red, 1.8–2 × 0.2–0.3 cm, puberulous; tepals 6, white to pinkish-white, puberulous on outer surface and glabrous on inner surface; outer tepals 4, obovate, 1–1.1 × 0.3–0.4 cm, apex slight acute to obtuse, margin entire; inner tepals 2, oblong to oblanceolate, longer than outer tepals, 1.2–1.3 × 0.2–0.3 cm, apex rounded, margin entire; styles 3, yellow, 2–3 mm long, free, stigmas 2-lobed, with twisted band; ovary red, obovate or turbinate, 1–1.1 cm long, 0.5–0.6 cm in diam., red, densely puberulous, wings not fully developed; placentation axile, 4-loculed, placentae partly branching 2 each locule. Fruits berry-like, obovate or turbinate, 1.4–1.5 cm long, 0.7–0.8 cm in diam., red, wingless or 4-ribbed, gray puberulous, apex beaked.

Etymology: —The specific epithet refers to Ta Dung, a national park of Dak Nong province, southern Vietnam in which the new species was found.

Phenology: —Flowering was observed from March to May. Fruiting may start from May to June.

Distribution and ecology: —The new species is currently known from Ta Dung National Park, southern Vietnam and probably also occurs in adjacent areas. The new species grows on the humid, moist rocky banks of streams in broad-leaved evergreen forests, at elevations of ca. 750 m, together with the dominant plants of Araliaceae ( Schefflera heptaphylla (L.) Frodin), Rutaceae ( Euodia calophylla Guillaumet ), Rutaceae ( Actinodaphne sesquipedalis Hook. f. & Thomson ex Meisn. ), Annonaceae ( Fissistigma polyanthoides (A.DC.) Merr. ), Urticaceae ( Elatostema spp. ), Rubiaceae (Urophyllym spp.), Myrtaceae ( Syzygium spp. ), and Dioscoreaceae ( Tacca spp. )

Conservation status:—Only one small-sized population with a few seedlings of Begonia tadungensis was found in the buffer zone of Ta Dung National Park, which are almost entirely covered by secondary forest. Furthermore, the local farmers continue to impose strong pressure on these forest patches, converting it mostly into coffee plantations. Thus, the persistence of the species might be at risk in the near future. This species is primarily assessed as Critically Endangered (CR B2ab(iii), C1, D) according to the IUCN categories and criteria ( IUCN 2019).

Notes:— Begonia sect. Platycentrum is distributed mainly in Himalayan regions ( Bangladesh, Bhutan, S.W. & S. China, N. India, N. Myanmar, Nepal, and N. Pakistan), extending to mainland Southeast Asia ( Laos, Malaysia, S. Myanmar, Thailand and Vietnam), and its adjacent islands ( China and Indonesia) ( Moonlight et al. 2018, Shui et al. 2019). Recent enumerations and discoveries (e.g. Doorenbos et al. 1998, Sands 2001, Kiew 2005, Nguyen & Tebbitt 2006, Girmansyah 2008, Phutthai et al. 2009, Hughes & Girmansyah 2011, Camfield & Hughes 2018, Chen et al. 2018a & b, 2019, 2020, Shui et al. 2019) indicate that there are ca. 178 species in this section ( Hughes et al. 2015 –). Moonlight et al. (2018) not only synonymise B. sect. Sphenanthera and B. sect. Monopteron with B. sect. Platycentrum , but also distinguished the members of the section with the berry-like fruits in the informally named “ Sphenanthera group” of B. sect. Platycentrum . Of these, eleven species of the “ Sphenanthera group” are currently recorded for the flora of Vietnam, i.e. B. longifolia Blume (1823: 102) , B. acetosella Craib (1912: 153) , B. balansana Gagnepain (1919: 194) , B. handelii Irmscher (1921: 24) , B. ceratocarpa Shui & Huang (1999: 13) , B. longicarpa Guan & Tian (2000: 131) , B. hahiepiana Nguyen & Tebbitt (2006: 374) , B. albopunctata , B. erectocarpa Chen et al. (2018a: 71) , B. pendens Chen et al. (2020: 94) , and B. satelloides Chen et al. (2020: 96) . The new species is here described raising the species number of the “ Sphenanthera group” within the section Platycentrum occurring in Vietnam to twelve.

Begonia tadungensis is clearly different from many of the berry-like fruited species of section Platycentrum occurring in India, Bhutan, Nepal, Bangladesh, Myanmar, Thailand, China, Malaysia, and Indonesia (e.g. B. acetosella Craib , B. lancangensis Huang (1999: 13) , B. aptera Blume (1827: 97) , B. pseudoheydei Chen et al. (2019: 29) , B. multangula Blume (1827: 96) , B. robusta Blume (1827: 96) , B. obovoidea Craib (1930: 413)) in its rhizomatous creeping habit (vs. with an erect stem). The new species is more similar to B. albopunctata in having broadly ovate leaves, three free styles, 4-loculed ovary, and berry-like fruits with beaked apex, but differs clearly from the latter in abaxial leaf surface, breeding system, peduncle length, pedicel length of staminate flower, pedicel length of pistillate flower, number of tepals of pistillate flower, shape and hairiness of fruits. Besides, it is also similar to B. pendens in its broadly ovate leaves and breeding system, but differs mainly from the latter in abaxial leaf surface, peduncle length, structure of pistillate flower, number of ovary locules, and shape, colour of fruits. Detailed comparisons of the new species and its two similar species are shown in Table 1.

Additional specimen examined (paratype):— VIETNAM. Lam Dong province: km 150 on way from Sai Gon to Da Lat, alt. 150 m, 26 March 1954, M. Schmid s.n. (P00539132).