Begonia dieuanhiae T.S.Hoang & C.W.Lin, 2022

HOANG, THANH SON & LIN, CHE-WEI, 2022, Two new species, Begonia minhaniae and B. dieuanhiae (sect. Platycentrum, Begoniaceae), from northwestern Vietnam, Phytotaxa 572 (1), pp. 87-96 : 92

Begonia dieuanhiae T.S.Hoang & C.W.Lin , sp. nov. § Platycentrum ( Figs. 4 & 5 )

Type:— VIETNAM: Son La province, Moc Chau District, Xuan Nha Nature Reserve , 20.702981N, 104.714297E, 748 m elevation, 14 August 2021, flowers and fruits, Hoang Thanh Son 9014 (Holotype VAFS; Isotypes VNMN) .

Monoecious rhizomatous herb. Rhizome stout, to 10 cm or longer, 5−8 mm thick, internodes congested 2−7 mm long, densely bright reddish-brown tomentose or woolly; leafless erect stem seen only at anthesis, up to 4 nodes, internodes 1–15 mm long, 3–5 mm thick, subappressed bright reddish-brown tomentose. Stipules persistent, reddish-brown to dusky red, triangular to widely triangular, 5–8 × 5–7 mm, herbaceous, strongly keeled, abaxially densely subappressed bright reddish-brown tomentose, margin entire, apex aristate, arista ca. 2.5 mm long; stipules of erect stem narrowly triangular to ovate, 4–6 × 2.5–5 mm, abaxially sparsely bright reddish-brown tomentose, margin denticulate, ciliate. Leaves alternate, petiole terete, red, 13−22 cm long, 3.5−6 mm diameter, densely subappressed bright reddish-brown tomentose or woolly; leaf blade asymmetric, oblique, ovate, elliptic to obovate, 11−19 × 6.5–12.6 cm, broad side 4–7.7 cm wide, basal lobes cordate, 1.5–4 cm long, apex acuminate to caudate, margin slightly reflexed and subentire with a line of reddish-brown tomentose or sericeous; leaf chartaceous, succulent, adaxially green, glabrous or very sparsely brownish-yellow appressed sericeous, glabrescent, abaxially pale green, veins brownish-red, glabrous except on veins; venation basally ca. 7 palmate, midrib distinct, ca. 3 secondary veins on each side, other primary veins branching dichotomously or nearly so, tertiary veins reticulate, densely appressed reddish-brown sericeous. Inflorescences terminal, bisexual, cymose arising directly from a short erect stem, up to 3 orders of branching; peduncle red, 6.5–11 cm long, sparsely yellowish-brown sericeous or tomentose. Bracts caducous, yellowish-red to pink tinged crimson, at basal node of inflorescence narrowly ovate, ca. 7 × 3.5 mm, abaxially brown sericeous or tomentose, margin ciliate or with a line of pilose. Staminate flower: pedicel pink, 15–25 mm long, sparsely pink tomentose, tepals 4, pinkish-white to rosy pink, outer 2 widely ovate to narrowly ovate, 15–25 × 13–17 mm, abaxially and margin sparsely tomentose, margin entire, apex obtuse to rounded; inner 2 oblanceolate to obovate, 13–16 × 4–10 mm, glabrous, apex obtuse to roumded; androecium zygomorphic, ca. 5 mm across; stamens golden yellow, 28–43; filaments ca. 1.5 mm long, fused at base; anthers obovate, ca. 1 mm long, 2-locular, apex rounded. Pistillate flower: pedicel pinkish-yellow to red, ca. 10 mm long, very sparsely tomentose, tepals 5, rosy pink, outer 2 widely obvate to elliptic, 13–17 × 8–10 mm, abaxially glabrous or with very sparsely tomentose, margin entire, apex rounded, inner 3 obvate, 12–14 × 5–8 mm, glabrous, apex obtuse to rounded; ovary trigonous-globose, ca. 7 mm long, 7 mm thick (wings excluded), rosy pink to yellowish-red, subglabrous; 3-winged, wings unequal, pink to red, subglabrous, margin entire; lateral wings narrower, very narrowly crescent-shaped, ca. 3 mm wide, abaxial wing narrowly crescent-shaped, ca. 5 mm wide; ovary 3-locular, placenta bilamellate; styles 3, shortly fused at base, orange to golden yellow, U-shaped, ca. 3.5 mm long, stigma spirally twisted. Capsule not seen.

Distribution and ecology:— Begonia dieuanhiae is endemic to Xuan Nha Nature Reserve, Moc Chau District, Son La province. On damp mossy vertical cliff faces, in shady broad-leaved evergreen forests, elevation 750–1,000 m.

Etymology:— The species’ epithet is in honour of the first author’s first daughter, Ms. Dieu Anh Hoang, who always supports the first author’s researches.

Conservation status:— The known locations of B. dieuanhiae are within the Xuan Nha Nature Reserve. There were only eight populations found at the site of collection with the number of mature individuals being less than 200. However, the forest reserve appears to have remained reasonably intact, we consider an IUCN category of Least Concern as long as the species’ distributions remain intact from disturbance.

Notes: In its ovate green foliage, 4-tepaled staminate flowers with zygomorphic androecium and 3-locular ovary, the new species mostly resembles B. phouchomvoyensis . However, B. dieuanhiae is distinct from B. phouchomvoyensis in its erect stem seen only at anthesis (vs. lacking erect stem), the petiole densely covered with subappressed bright reddish-brown tomentose or woolly (vs. red villous), pistillate flowers with 5 tepals (vs. 3-tepaled), ovary wings narrowly crescent-shaped (vs. triangular), and rounded distally (vs. tip pointed). A comparison of B. dieuanhiae and B. phouchomvoyensis is presented in Table 2 .

Figures

FIGURE 4. Begonia dieuanhiae T.S.Hoang & C.W.Lin. A. Habit; B, B’. Portion of leaf, upper and lower surfaces; C. Stipule of rhizome, C’. stipule of erect stem; D, D’. Bracts; E, E’. Staminate flower, face and side views; F, F’, F’’. Stamens, dorsal, ventral and side views; G, G’. Pistillate flower, face and side views; H, H’. Style and stigmatic band, dorsal and ventral views; I. Cross section of an immature capsule.

FIGURE 5. Begonia dieuanhiae T.S.Hoang & C.W.Lin.A, B. Habit and habitats; C.Abaxial leaf; D. Young leaf; E, F. Rhizome and erect stem, also showing stipules and petioles; G. Portion of leaf, upper surface, H. same, lower surface; I. Erect stems and inflorescence; J. Staminate flower, face and back views; K. Pistillate flowers, face view, L. same, side view; M. Cross section of ovary.