Begonia sohoton 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 : 265-267

1. Begonia sohoton Rubite, C. Justo, P. Villaseñor & C.W. Lin , sp. nov. ( Figs. 2 & 3 )

Type:— PHILIPPINES. Samar Island, Province of Samar, Municipality of Basey, Sohoton Caves and Natural Bridge National Park , elevation 120 m, 11°21′31′′N, 125°9′29′′E, 7 December 2018, R . Rubite 997 (holotype PNH) .

Monoecious perennial herbs. Stem maroon with white spots, prostrate, 15–26 cm long, 10–15 mm in diameter, internodes 3−5 mm long, tomentose (10−13 mm, brown). Stipules persistent, cream, triangular, 18–25 × 12–20 mm, herbaceous, strongly keeled and tomentose, margin entire, apex aristate. Leaves alternate, petiole terete, 12−18 cm long, 6−10 mm thick, pale green when young, brownish when mature, tomentose (12−17 mm, brown); leaf blade asymmetric, oblique, widely ovate, 9−18 × 8–15 cm, basal lobes cordate, apex acuminate, margin almost entire, ciliate with brown hairs (2.5−4 mm); leaf blade subcoriaceous, succulent, adaxially dark green, waxy, with brown hairs (7−12 mm), glabrescent; abaxially pale green, tomentose (7−8 mm), primary veins 8–10. Inflorescence axillary, bisexual, cymosely branching panicle 25–36 cm long, arising directly from rhizome, branching 5–6 times, ascending, peduncle 16–27 cm long, green, tomentose (3−5 mm brown); protandrous. Bracts white to pinkish, hyaline, deciduous, glabrous, those at the basal node of the inflorescence wide ovate, boat-shaped, ca. 5 × 8 mm, apex acute, margin entire; bracts at the summit of the inflorescence similar but smaller. Staminate flower: pedicel ascending, pink, 10−15 mm long with sparse pinkish hairs; tepals 2+2 glabrous, outer pair white, orbicular 8–15 × 8–14 mm, inner pair white, obovate 6–10 × 3–6 mm; stamens 20–25; filaments 1 mm long united at the base; anthers yellow, obovate, apex rounded ca. 1 mm long. Pistillate flower: pedicel horizontal later drooping, pale green to pink 1.5–2.2 cm long with sparse brownish hairs; tepals 2+2 glabrous, outer pair white, orbicular 8–15 × 8–12 mm, inner pair white, obovate 6–10 × 3–5 mm; ovary creamy white to pink, ovoid, 7–10 × 5–7 mm (wings excluded), generally glabrous but with dense brownish hair at the base becoming sparse along the pedicel, wings 3, unequal, falcate, arching towards the apex 3–6 mm long, lateral wings shorter 4–9 mm wide, abaxial wing 9–15 mm wide, with sparse hairs to nearly glabrous, ovary 3-locular, placenta axile, bilamellate; styles 3, yellow, ca. 3 mm long, stigma spirally twisted. Capsule pendent, pedicel 1.8–2.5 cm long, tepals deciduous; 8–10 × 32–45 mm (wings included), green or dusky pink when fresh; wings 3, falcate, unequal, 5–7 mm long; lateral wings 12–16 mm wide, abaxial wing 18–23 mm wide.

Diagnostic characters:— A combination of tomentose rhizomes, petioles, peduncles and stipules with falcatewinged capsules is unique to Begonia sohoton among all species in Begonia sect. Baryandra .

Etymology: — The species is named after the locality Sohoton River where the new species was discovered. Sohoton comes from a local word “sohot” meaning to pass through a narrow passage; this was also a characteristic of B. sohoton which arises from tiny crevices of the limestone walls.

Distribution and habitat:— B. sohoton is known only from the towering and very rugged karst cliffs which line the Sohoton River. It occurs on a semi-exposed rocky slope above river water, at 120 m elevation,

Proposed Conservation Status: — B. sohoton is known only from the type locality in Basey, Samar. Although the area is under protection as a national park, habitat disturbance brought about by human activities such as tourism and the construction of a hanging walkway at the limestone cliffs may have a negative impact on the species. Therefore , following the IUCN criteria B. sohoton is hereby proposed as Vulnerable ( VU D2 ) ( IUCN Standards and Petitions Committee, 2019) .

Figures

FIGURE 2. Begonia sohoton 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, dorsal and ventral views; G, G’. Pistillate flower, face and side views; H, H’. Style and stigmatic band, dorsal and ventral views; I. Capsule; J, J’. Cross sections of an immature capsule. All from R. Rubite 997.

FIGURE 3. Begonia sohoton Rubite, C.Justo, P.Villaseñor & C.W.Lin. A, B. Habit and habitats; C. Portion of leaf, upper surface, D. Lower surface, also showing peduncle; E. Stipules; F. Petioles; G. Inflorescence, also showing capsules; H. Immature pistillate flower; I. Staminate flower.A, field photograph; B to I from R. Rubite 997.