Begonia rolandfadlii Dayanti, Ramadanil & D.C.Thomas, 2020

Dayanti, Eka P., Pitopang, Ramadanil, Ardi, Wisnu H. & Thomas, Daniel C., 2020, Two New Species of Begonia (Begoniaceae, Section Petermannia) from Mount Sidole, Central Sulawesi, Indonesia, Phytotaxa 439 (2), pp. 136-142 : 140-141

2. Begonia rolandfadlii Dayanti, Ramadanil & D.C.Thomas , spec. nov.

Section Petermannia

Diagnosis: —Because of a similar growth habit, the narrow leaf lamina and pinnate venation, and similar inflorescence morphology, Begonia rolandfadlii resembles Begonia cuneatifolia Irmscher (1913: 370) , but it differs from this species by the serrate or double serrate to shallowly lobed leaf lamina margin, an adaxial leaf lamina surface with distinctly sunken primary and secondary veins and a sparse indumentum of bristly hairs between the veins, smaller male flower tepals (5–6 × 6–7 mm), and fewer stamens (ca. 21–25). Begonia cuneatifolia has an entire leaf lamina margin or sometimes the margin is serrulate to serrate in the distal third of the lamina, the adaxial leaf surface is glabrous and the veins are not sunken, the male flower tepals are larger (10 × 11 mm), and the androecium is comprised of more stamens (ca. 40 stamens).

Type: — INDONESIA. Sulawesi, Central Sulawesi: Gunung Sidole, Aloo Village , 26 December 2018, E. P. Dayanti ED 9 (holotype BO!; isotype CEB!) .

Perennial, monoecious herb, up to ca. 35 cm tall. Stem erect, branched, internodes 2–5 cm long, reddish-brownish, with microscopic glandular hairs and a moderately dense indumentum of multicellular bristly hairs. Leaves alternate; stipules persistent, ovate to narrowly ovate, 7–10 × 3–4 mm, reddish-greenish, glabrous, midrib prominent, margin entire, apex narrowed into bristle up to 3 mm long; petioles 5–6 mm long, reddish-brownish, terete, hairy; lamina basifixed, narrowly elliptic, 4–8 × 1–2.7 cm, asymmetric, base asymmetric, lobes not overlapping, apex acuminate, margin double serrate to moderately lobed (up to ca. 50% of lamina width), teeth bristle-pointed, adaxial surface green, sparsely hairy with bristles between the veins, abaxial surface pale green, hairy on the veins; venation pinnate, with 4–5 secondary veins on each side, primary and secondary veins distinctly sunken on the adaxial surface, prominent on the abaxial surface. Inflorescences axillary, protogynous; female flowers solitary (female inflorescence one-flowered), one node basal to male inflorescence part or further separated, peduncle ca. 1 mm long, pale green, glabrous; male inflorescence paniculate-cymose, strongly compressed, composed of up to three compressed simple monochasia, each simple monochasium with 2−4 flowers; peduncle ca. 1 mm long, reddish, sparsely hairy; bracts stipule-like, persistent, ovate, ca. 8 × 3 mm, translucent, midrib slightly prominent, red, glabrous, margin entire, apex acuminate and narrowed into bristle ca. 1 mm long; bracteoles persistent, ca. 2–3 × 1 mm, ovate to narrowly ovate, translucent, midrib red. Male flowers: pedicels 4–5 mm long, white, glabrescent; tepals 2, white, broadly ovate, 5–6 × 6–7 mm, abaxial surface sparsely hairy, margin entire, apex rounded; androecium yellow, stamens ca. 21–25, free filaments up to ca. 1.5 mm long, fused at the base, anthers ca. 0.5–1 mm long, dehiscing through unilaterally positioned slits ca. ½ as long as the anthers. Female flowers: pedicels 3–4 mm long, pale green; tepals 5, white, unequal, one smaller, obovate, ca. 4 × 2 mm, the other four larger, ovate, 7–9 × 4.5–5 mm, abaxially glabrous, margin entire, apex acute; ovary ellipsoid, ca. 7 × 3 mm (excluding wings), pale green, glabrescent, locules 3, placentae bilamellate, wings 3, equal, base rounded, apex truncate, widest point up to 4 mm (apically); style ca. 0.5–1 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruits: peduncles ca. 0.5–1 mm long; pedicels up to ca. 1 mm long; seed-bearing part ellipsoid, 4.5–7 × 3.5–4 mm (excluding the wings), wing shape as for ovary, widest point up to ca. 5 mm. Seeds barrel-shaped, ca. 0.2–0.3 mm long.

Habitat: —Primary forest, terrestrially on steep slopes with thick leaf litter layer, in dense shade, at ca. 930 m elevation.

Distribution: — Central Sulawesi, Sulawesi, Indonesia. Known from only Gunung Sidole.

Etymology: —This species is named in honour of Roland Putra Pribadi Ahmad and Zulfadli, who helped as guides and to collect the specimens.

Notes: —Short petioles in combination with narrow leaf laminas with pinnate venation are not uncommon in Begonia section Petermannia [e.g. the Bornean Begonia xiphophylla Irmscher (1953b:100 ; see Sang et al. 2015 for a detailed description and illustration), B. xiphophylloides Kiew ( Julia et al. 2013: 31) and B. tenuissima Julia & Ling ( Julia & Ling, 2015: 125) ], the New Guinea [e.g. Begonia malmquistiana Irmscher (1913: 337) ] and the Philippines [e.g. Begonia brevipes Merrill (1912: 378) ], but this character combination is rare in Sulawesi begonias and can be found only in the allied species Begonia cuneatifolia from Gorontalo and North Sulawesi (see diagnosis).

Provisional conservation assessment: —VuD2, Vulnerable. Begonia rolandfadlii is known from only a single collection from Gunung Sidole. The forest at the type locality is not legally protected, but it is in good condition and currently there are no signs of anthropogenic threats. However, due to the restricted distribution and limited number of observed mature individuals, this species may be prone to stochastic effects and natural disasters such as tree falls and landslides.