Begonia tarangban Rubite, C. Justo, P. Villaseñor & C.W. Lin, 2021

Rubite, Rosario Rivera, Justo, Celeena Aimeree De Guzman, Villaseñor, Patricka Coliflores, Delos Angeles, Marjorie D., Tandang, Danilo N. & Lin, Che-Wei, 2021, Three new species of Begonia (section Baryandra, Begoniaceae) from Samar Island, the Philippines, Phytotaxa 516 (3), pp. 263-274 : 267-269

2. Begonia tarangban Rubite, C. Justo, P. Villaseñor & C.W. Lin , sp. nov. ( Figs. 4 & 5 )

Type:— PHILIPPINES. Samar Island, Province of Samar, City of Calbayog, Tarangban Falls , growing along the shaded moist rocks and soils surrounding the falls, elevation 160 m, 12°15′7′′N, 124°23′56′′E, 9 December 2018, R . Rubite 998 (holotype PNH) .

Monoecious perennial herbs. Stem green to brown, sparsely hirsute (hairs 1–3 mm, light brown) prostrate, 25–43 cm long, 5–8 mm in diameter, internodes 4–6 cm. Stipules persistent, pink, asymmetrically ovate-triangular, 11–14 × 9–14 mm, strongly keeled and hirsute abaxially with a tuft of fimbriae at the base, margin entire, apex aristate. Leaves alternate, petiole terete, brown 14−18 cm long, 5−7 mm thick, lanate (1–3 mm whitish); blade obliquely ovate, 9–14 × 7–12 cm, apex attenuate, base cordate, margin shallowly undulate almost entire; leaf blade thickly chartaceous, adaxial surface green with darker green to almost black veins, glabrous, abaxial surface maroon with sparse hairs on veins, veins brownish green, pilose (1–2 mm whitish), primary veins 6–8. Inflorescence 23–32 cm long axillary, arising directly from the rhizome, dichotomously branching ca. 4 times; peduncle light brown, erect, 17–25 cm long, 4–6 mm in diameter, glabrous; pedicels 10–12 mm erect to ascending in staminate flowers, horizontal in pistillate flowers. Bracts (residual) creamy green to pinkish, hyaline, deciduous, glabrous, wide ovate, boat-shaped, apex acute, margin entire. Staminate flowers: tepals 2+2 glabrous, outer upper lobe adaxial surface pinkish white abaxial surface reddish, orbicular, lower lobe white 11–13 × 10–12 mm, inner pair white, obovate 9–12 × 4–5 mm; stamens 25–35; filaments 0.5 mm long united at the base; anthers yellow, obovate, apex rounded ca. 1 mm long. Pistillate flowers: tepals 2+2 glabrous, outer upper lobe adaxial surface pinkish white abaxial surface reddish, orbicular, lower lobe white 10–12 × 9–11 mm, inner pair white, obovate 9–11 × 4–5 mm; ovary elliptic, green with pink outline 8–10 × 4–5 mm, three-locular, placentae axile, bilamellate; styles three, 5 mm long, stigma yellow; wings unequal, triangular, abaxial wing 8–10 × 4–6 mm, lateral wings 8–10 × 3–4 mm, apex truncate, base acute to rounded, glabrous; Capsule nodding, pedicel 1.0– 1.5 cm long, tepals deciduous; 12–15 × 10–12 mm (wings included).

Etymology: — Named after the Tarangban Falls, where the new species was discovered.

Distribution and habitat:— B. tarangban is endemic to Tarangban Falls, Calbayog City, Samar Island. It grows on semishaded rocky slopes near the falls at 160 m in elevation.

Notes:— B. tarangban is similar to B. biliranensis in having ovate stipules, obliquely ovate, strongly inequilateral cordate leaves where adaxial surface is glabrous and abaxial surface is associated with hairs at the veins; long petioles (11–18 cm); long inflorescence dichotomously branching 4 to 5 times. However, the new species differs in having long internodes 4−6 cm (vs. crowded leaves); stipules hirsute abaxially with a tuft of fimbriae at the base (vs. glabrous); smaller lamina (9–14 × 7–12 vs. 15–22 × 10–15); longer peduncle (17–25 vs. 11–18 cm); larger flowers (22–26 × 19–24 vs. 11–12 × 11–12 mm); capsule wings unequal (vs. equal) and wings triangular (vs. rounded).

Proposed Conservation Status:— B. tarangban is known only from the type locality in Tarangban Falls, Calbayog City. Although the area is protected as part of the Samar Island Natural Park, habitat disturbance brought about by human activities such as tourism may have a negative impact on the species. Therefore , following the IUCN criteria B. tarangban is hereby proposed as Vulnerable ( VU D2 ) ( IUCN Standards and Petitions Committee, 2019) .

Figures

FIGURE 4. Begonia tarangban Rubite, C.Justo, P.Villaseñor & C.W.Lin. A. Habit; B, B’. Portion of leaf adaxial and abaxial surfaces; C. Stipule; 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, dorsal and ventral views; I. Capsule; J. Cross section of an immature capsule. All from R. Rubite 998.

FIGURE 5. Begonia tarangban Rubite, C. Justo, P.Villaseñor & C.W.Lin.A, B. Habit and habitats; C. Stipule; D. Petiole; E. Rhizome; F. Portion of leaf, upper surface, G. same, lower surface; H. Inflorescences; I. Staminate flower; J. Pistillate flower; K. Capsule; L. Cross section of an immature capsule.All from R. Rubite 998.