Begonia dakrongensis C.H.Nguyen, T.A.Le & C.W.Lin

Nguyen, Cuong Huu, Le, Anh Tuan, Ha, Van Bac & Lin, Che Wei, 2024, Begonia dakrongensis (Begoniaceae), a new species from Dakrong Nature Reserve, Quang Tri province in Central Vietnam, Phytotaxa 645 (1), pp. 85-90 : 86

Begonia dakrongensis C.H.Nguyen, T.A.Le & C.W.Lin , sp. nov. ( Figs. 1 & 2 )

Type:— VIETNAM. Quang Tri province, Dakrong district, Huc Nghi commune, Dakrong Nature Reserve , around point 16°27’46.9”N, 107°05’32.4”E, common in the moist shady areas under evergreen primary evergreen forest on the rocky crevices in association with of waterfall Do Quyen at elevations of about 800 m a.s.l., 26 May 2023, Tuan Anh Le, Ha Van Bac, LTA.DKR.09 (holotype VNMN B0000608 !; isotype VNF 20230526010 !)

Rosette, rhizomatous perennial herbs, monoecious. Rhizomes dusky magenta to reddish-brown or brownish-green, terete, to 6 cm or longer, 4–7 mm across, creeping, sparsely villous-hirsute, internodes 1.5–9 mm long. Stipules ovate-triangular, slightly oblique, 5–8 × 3.5–4.5 mm, glabrous or very sparsely hirsute, apex attenuate and aristate, arista 0.8–3 mm long, margin entire or very sparsely denticulate. Leaves alternate, nearly pressed to substrate; petiole dusky red, 1.3–3.5 cm long, 2.5–4 mm across, grooved above, sparsely to densely villous-hirsute, leaf blade asymmetric, not oblique or nearly so, obtriangular-spathulate to oblong-obovate or widely obovate, 4.7–17 × 3–12 cm, base obliquely cordate, lobes 6–12 mm long, broad side 2–7.3 cm wide, margin denticulate on the upper two-thirds and subentire to repand on the lower one-third, slightly revolute and undulate with rows of sparsely white villous and red scabrous, sometimes with coarsely dentate and irregularly angular, apex acuminate to acute; leaf subcoriaceous, succulent, adaxially emerald green, glabrous, waxy, abaxially pale green, veins pink to red, sparsely pinkish-white villous-hirsute and red scabrous; venation palmate-pinnate, midrib distinct, 2 or 3 secondary veins on broad side and 0 or 1 on narrow side, lateral through connection between with other basal veins, minor veins inconspicuous. Inflorescence axillary and terminal, unisexual or bisexual, cymose-paniculate or racemose, 1.5–3 cm long, rose pink to red, erect, glabrous or subglabrous; Bracts creamy pink to creamy white or greenish-white, hyaline, persistent, ovate-triangular to widely triangular or narrowly triangular, the first pair up to 7 × 4.5 mm, decreasing in size towards the more distal inflorescence nodes, attenuate and aristate at apex, arista 0.5–2.5 mm long, margin denticulate; Pistillate flower produced from a very short peduncle at the basal node of the inflorescence, usually solitary; staminate flowers produced in distal inflorescence part, in several 1–3-flowered compressed monochasial partial inflorescences borne on lateral branches (2–12 mm). Staminate flower: pedicel 10–14 mm long, tepals 4, outer 2 white to pinkish-white, sometimes with pale greyishpink veins, orbicular to obovate, 7–12 × 8.5–10 mm, margin entire, abaxially red scabrous; Inner 2 white or pinkish-white, oblanceolate, apex round, base cuneate, 7.5–9 × 2–3 mm, glabrous; Androecium actinomorphic, stamens ca. 25, yellow, filaments free, ca. 0.4 mm long, anthers widely obovate, ca. 0.7 mm long, 2-locular, apex retuse. Pistillate flower (immature): subsessile, tepals 5, white or pinkish-white, outer 4 tepals widely ovate to oblong, margin entire, apex rounded to obtuse, abaxially red scabrous; inner 1 obovate to oblanceolate, glabrous; Ovary trigonous-globose, densely red scabrous, 3-locular, 3-winged, wings subequal, trapeziform, truncate to broadly acute proximally, pointed distally, placentation axle, bilamellate; styles 3, Y-shaped, divided to base, stigmatic band spiralled. Capsule pedicel ca. 1 mm long, body trigonous-globose, 10–11 × 12–14 mm long (wings included).

Distribution and ecology: —The new species is only known from Dakrong Nature Reserve, in Quang Tri province, Central Vietnam. Begonia dakrongensis usually grows in moist shady places near waterfalls, along streams and occasionally on the rocky crevices covered by evergreen broad-leaved forests at elevations of about 800 m a.s.l.

Etymology: —The specific epithet refers to the type locality (Dakrong Nature Reserve, Central Vietnam.).

Conservation status: —The new species is known from a single collection, and we do not have information about its abundance at type locality its conservation status is assessed as Data Deficient ( DD; IUCN 2022 ).

Notes: —Among the rhizomatous begonias in Vietnam, Begonia dakrongensis closely resembles B. abbrevata and B. eberhardtii Gagnepain (1919: 198) in their axillary and terminal inflorescence with densely bracts and flower structure, but these three species differ in many morphological characteristics. A detailed comparison is provided in Table 1 .

Figures

FIGURE 1. Begonia dakrongensis C.H.Nguyen, T.A.Le & C.W.Lin. A. Habit; B, B'. Portion of leaf, upper and lower surfaces; C. Stipule; D, D', D'', D'''. Bracts; E, E'. Staminate flower, face and side views; F, F'. Stamens, ventral and dorsal views; G, G'. Immature pistillate flower, face and side views; H, H'. Style and stigmatic band, ventral and dorsal views; I. Cross section of ovary; J. Capsule.

FIGURE 2. Begonia dakrongensis C.H.Nguyen, T.A.Le & C.W.Lin.A. Habit and habitat; B. Habitats; C. Inflorescence, showing bracts, immature staminate flowers and capsule; D. Portion of leaf, upper surface, E. same, lower surface; F. Staminate flowers; G. Immature staminate flower; H. Staminate flower, face view; I. Immature pistillate flower; J. Cross section of ovary; K. Capsule.