Begonia jubar V.T.Pham & C.W.Lin, 2021

Pham, Van The, Dinh, Quang Diep, Nguyen, Van Canh, Trinh, Ngoc Bon, Nguyen, Duc Dinh, Nguyen, The Hien & Lin, Che Wei, 2021, Begonia of Vietnam: an updated checklist, including a new species and a new record, Phytotaxa 507 (2), pp. 144-154 : 145-148

Begonia jubar V.T.Pham & C.W.Lin , sp. nov. §. Petermannia ( Figs. 2 & 3 )

TYPE:— VIETNAM. Dak Lak Province: Lak district, Nam Ka commune, Nam Ka Nature Reserve , semi-deciduous lowland forest on silicate rocks, around point 12°27.949’ N, 108°05.851’ E, at elevation 450 m a.s.l., 11 September 2019, Dinh Quang Diep, Nguyen Duc Dinh, Nguyen The Hien, NK 34 (Holotype: SGN; Isotypes: HNU, TAIF).

Monoecious rhizomatous herb. Rhizome stout, creeping, yellowish-green, ca. 1 cm thick, internodes 0.5–1.5 cm long, densely hirsute. Stipules persistent, rose pink, widely triangular, recurved, (0.5–) 0.8–1.2 cm long, (0.7–) 1–1.5 cm wide, herbaceous, keeled, glabrous, margin entire, apex aristate, arista 0.5–2 mm long. Leaves alternate, petiole terete, carmine to pale vermilion, (6−) 12−30 cm long, 0.3−0.5 cm thick, glabrous, erect or ascending; leaf blade asymmetric, oblique, ovate to widely ovate, slightly polygonal in outline, 9−18 cm long, 6.3–14.5 cm wide, broad side 3.5–8 cm wide, basal lobes cordate, 2.3–4.5 cm long, glabrous, margin denticulate to subentire, apex acuminate, sometimes undulate; leaf thin coriaceous, succulent, adaxially yellowish-green to emerald green, greyish-white to pale green zone along primary and secondary veins, dark maroon to blackish green patches between veins; abaxially pale green, purplish-red between primary and secondary veins; venation basally ca. 7 palmate, midrib distinct, ca. 2 secondary veins on each side, tertiary veins reddish, lateral through connection between with other basal veins, minor veins reticulate. Inflorescences axillary, dichasial cymes, arising directly from rhizome, branched 3–5 times; peduncle olive green to crimson, to 55 cm long, glabrous, sometimes with sparsely hirsute on upper half. Bracts deciduous, yellowgreen, dusky red toward base, ovate to very widely ovate, first pair ca. 1.5 cm across, glabrous, margin denticulate to serrate with puberulous, bracts of upper inflorescence similar but smaller. Staminate flower: pedicel 1.5–2 cm long, glabrous, tepals 4, pinkish-white, glabrous, outer 2 very widely ovate to suborbicular, 1.5–2.4 cm long, 1.6–2.3 cm wide, inner 2 lanceolate to narrowly elliptic, 1–1.3 cm long, 0.5–0.6 cm wide; androecium actinomorphic or nearly so, ca. 0.7 cm across; stamens golden yellow, 30–45; filaments fused at base into a column ca. 1.5 mm long; anthers obovate, ca. 2 mm long, 2-locular, apex rounded, more or less equal at filaments. Pistillate flower: pedicel 1.5–2 cm long, glabrous, tepals 3, pinkish-white, glabrous, outer 2 suborbicular to widely depressed ovate, 1.5–1.7 cm long, 1.8–2.3 cm wide, inner 1 narrowly elliptic, 1–1.3 cm long, 0.5 cm wide; ovary narrowly trigonous-ellipsoid, 1–2 cm long, 0.4–0.7 cm thick (wings excluded), pink to white; 3-winged, wings unequal, rosy, 1.7–3 cm long, lateral wings narrower, narrowly triangular, 0.3–0.8 cm wide, abaxial wing triangular, 0.6–1.2 cm wide, margin entire; ovary 3- locular, placenta bilamellate; styles 3, fused at base, golden yellow, ca. 0.5 cm long, stigma spirally twisted. Capsule pendent on a stalk 1.7–2.5 cm long, capsule 2.4–3 cm long, 2.7–4 cm thick (wings included), anchor-like in outline, wings unequal, triangular.

Distribution and ecology: Begonia jubar is endemic to Lak district in Dak Lak Province, southern Vietnam. It grows on silicate cliff faces in semi-shade, at ca. 500 m elevation, under the canopy of trees species such as Canarium subulatum , Colona thorelii , Cratoxylum formosum , Dipterocarpus intricatus , Hopea odorata , Irvingia malayana , Lagerstroemia calyculata , Lithocarpus spp. , Magnolia mediocris , Schima superba , Spondias pinnata , Stereospermum chelonoides , S. tetragonum , Syzygium cumini , S. polyanthum , Vitex glabrata , V. pierreana , V. pinnata , Walsura robusta , Wrightia annamensis with average diameter of ca. 20–30 cm, and average height of ca. 15–20 m; shrub species composed of Aporosa villosa , Ardisia crenata , A. paniculata , Erioglossum rubiginosum , Psychotria asiatica, Croton cascarilloides, Chromolaena odorata with average height under 5 m. The herbaceous species sharing the habitat include Amomum longiligulare , Curcuma angustifolia , Lophatherum gracile , Ophiuros exaltatus , Tridax procumbens , and some other Poaceae sp., the habitat is highly disturbed by road construction.

Etymology:— From latin, jubar = brightness; referring to its outstanding bright veins that contrast with the dark lamina.

Conservation Status:— This species is not common in Nam Ka Nature Reserve, and it may be threatened by collections for horticulture trade in the future because of its beautiful leaves. Although the type location is in the protected area, the habitat around this area is disturbed due to current road construction. We consider a provisional IUCN category of Vulnerable is appropriate, under VUD2 .

Notes:— Begonia rigidifolia Aver. (2012:16) , an atypical member of sect. Petermannia based on Shui et al. (2019), is the species most closely allied to Begonia jubar . Thus, it would be most reasonable to assign B. jubar to sect. Petermannia based on its non-tuberous habit, axillary inflorescences, 3-locular ovaries and bilamellate placentae. B. jubar is similar to B. rigidifolia in having hirsute rhizomes, 4-tepaled staminate flowers and 3-tepaled pistillate flowers, and 3-locular ovaries with unequal wings. However, B. jubar is distinct in having glabrous (vs. hirsute) stipules and petioles, leaf base basifixed (vs. peltate), bract margin denticulate to serrate and puberulous (vs. long ciliate) and larger staminate flowers and pistillate flowers.A comparison of the salient characters of the two species is presented in Table 1.

Figures

FIGURE 2. Begonia jubar V.T.Pham & C.W.Lin. A. Habit; B. Rhizome, showing stipules; C, C’, C’’. Stipules; D-D’’’. Bracts; E, E’. Staminate flower, face and side views; F, F’. Stamens, ventral and dorsal views; G, G’. Pistillate flower, face and side views; H, H’. Style and stigmatic band, ventral and dorsal views; I. Cross section of an immature capsule.

FIGURE 3. Begonia jubar V.T.Pham & C.W.Lin. A, B. Habit and habitats; C, D. Leaves; E. Rhizome, showing stipules; F. Immature inflorescence, showing bracts; G. Inflorescence, showing flowers and capsules; H. Bracts; I. Staminate flower, face and side views; J. Pistillate flower, face and side views; K. Immature capsule; L. Cross section of an immature capsule.