Begonia austrovietnamica C. - I Peng, C. W. Lin, D. D. Nguyen & N. D. Truong, sp. nov.
Creators: name: Peng, Ching-I
name: Truong, Nguyen-Dong
name: Nguyen, Danh-Duc
name: Lin, Che-Wei
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Cucurbitales
Begoniaceae
Begonia
Begonia austrovietnamica

description: Begonia austrovietnamica C.-I Peng, C.W. Lin, D.D. Nguyen & N.D. Truong, sp. nov. —
TYPE: VIETNAM, Bình Thu ận province. Type specimens pressed from plants cultivated in the experimental Greenhouse of Academia Sinica, 16 October 2017, Ching-I Peng 25072 (holotype HAST).
NJflüdzḛ Figs. 1, 2
Monoecious tuberous herb. Stem acaulescent, tuberous at base, tubers globose or sub-globose up ca. 1 cm across, with numerous fibrous roots. Stipules pale green, triangular, 6–10 mm long, 3.5–6 mm wide, herbaceous, keeled, glabrous, margin entire, apex mucronate apiculate. Leaves alternate, held more or less horizontally; petiole terete, red, 7−22 cm long, 2.5−5 mm across, sparsely to densely white villous; leaf blades asymmetric, oblique, ovate to widely ovate, 8−19 cm long, 5.3–12.5 cm wide, broad side 3.5–7 cm wide, basal lobes cordate, 2.2–4 cm long, apex attenuate, margin denticulate and ciliate; leaf chartaceous, succulent, adaxially metallic grayish-green to dusky silvery, more or less variegated on the upper surface, with irregular, dark green to blackish green splash patch or semi-continuous spots of variable sizes, embellished with a blackish green band running parallel to the margin, adaxially puberulous; abaxially reddish to magenta, abaxially reddish to pale magenta, with crimson irregular splash patch and a band running parallel to the margin corresponding to the pattern on adaxial surface; villous or tomentose on all veins; venation basally ca. 7 palmate, midrib distinct, ca. 3 secondary veins on each side, tertiary veins lateral through connection between with other basal veins, minor veins reticulate. Inflorescences axillary, a bisexual cymosely branching panicle 4.5–19 cm long, rachis crimson, villous, inflorescence a racemose cyme, peduncle 3–13 cm long, branched 2 or 3 times, erect; protandrous. Bracts pale yellowish green, hyaline, persistent, widely triangular-ovate to triangular-lanceolate, 4–6 mm long, 2–5 mm wide, apex acute, glabrous, margin fimbriate. Staminate flower: pedicel 1–1.5 cm long, glabrous or very sparsely villous, tepals 4, white, outer 2 suborbicular to widely depressed obovate, ca. 1 cm long, 1–1.3 cm wide, abaxial hirsute; inner 2 narrowly obovate, 0.7–1 cm long, 0.3–0.5 cm wide, apex rounded; androecium zygomorphic, ca. 0.4 cm across; stamens yellow, 30–35; filaments shortly fused at base; anthers widely obovate, ca. 1 mm long, golf club-like, 2-locular, apex incised, more or less equal at filaments. Pistillate flower: pedicel 0.3–0.5 cm long, sparsely tomentose; ovary pale green, body very narrowly trigonous-ellipsoid or clavate, ca. 5 mm long, 2 mm thick (wings excluded), hirsute; 3-winged, wings equal, narrowly triangular, point at tip, narrowed to base, 0.9–1.5 cm long, 2–3 mm wide, margin entire; ovary 3-locular, placenta undivided; tepals 6, white, outer 3 ovate to obovate, 7.5–13 mm long, 5–6 mm wide, abaxial hirsute; inner 3 tepals obovate to narrowly obovate, 6–8 mm long, 3–4 mm wide; styles 3, short fused at base, yellow, ca. 2 mm long, stigma spirally twisted. Capsule pendent on a stalk ca. 1 cm long, capsule ca. 13–17 cm long, 12–15 mm thick (wings included), wings equal, narrowly triangular, point at tip, sometimes hooklike towed at the tip.
Distribution: Begonia austrovietnamica is endemic to southern Vietnam (Bình Thuận provice).
Etymology: Named for South Vietnam, where the new species was discovered.
Ecology and phenology: Rooting in soil pockets, moss or bare roots of other plants, on clefts in granite rock, well shaded to bright, in semi-deciduous forest at an altitude of 300– 500 m. Flowering at the type locality is from August to September. It is predicted that fruiting occurs from the end of September onwards and may last about two months.
Notes: Begonia austrovietnamica is one of the most beautiful Vietnam Begonia species, having impressive foliage decorated with metallic silvery patches, embellished by many dark spots and a band running parallel to the silver margin. Begonia austrovietnamica is most similar to B. alicida in being a tuberous species with a dormant period, having 4- tepaled staminate flowers and 3-locular ovaries. However, the new species differs from B. alicida in being stemless with basal leaves (vs. erect stem), having a strongly asymmetrical (vs. slightly asymmetrical) lamina, inflorescence axillary (vs. terminal), pistillate flowers 6-tepaled (vs. 5-tepaled), and ovary narrowly trigonous-ellipsoid (vs. trigonous-spheroid). Based on morphological characteristics, the new species is best assigned under section Alicida (Moonlight et al. 2018). B. austrovietnamica is also superficially similar to forms of Begonia bataiensis with variegated leaves, and both species grow in southern Vietnam, however our new species differs in having a larger (8–19 × 5.3–12.5 cm vs. 4.5–6 × 5–6.5 cm) and strongly asymmetrical (vs. symmetrical to slightly asymmetrical) lamina, pistillate flower tepals abaxially hairy (vs. glabrous), ovary narrowly trigonous-ellipsoid (vs. narrowly cylindrical) with 3 wings (vs. without wings), growing on granite cliffs (vs. limestone cliffs). Detailed comparison of the three species is presented in Table 1.
description: Published as part of Peng, Ching-I, Truong, Nguyen-Dong, Nguyen, Danh-Duc & Lin, Che-Wei, 2018, Begonia austrovietnamica (sect. Alicida, Begoniaceae), a handsome new species from South Vietnam, pp. 95-99 in Phytotaxa 381 (1) on pages 95-98, DOI: 10.11646/phytotaxa.381.1.12, http://zenodo.org/record/13726294