Begonia sidolensis Dayanti, Ramadanil & Ardi, 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 : 137-140

1. Begonia sidolensis Dayanti, Ramadanil & Ardi , spec. nov. ( Figures 1 & 2 )

Section Petermannia

Diagnosis: — B. sidolensis is a species from montane forest of Gunung Sidole, Sulawesi. It resembles Begonia gemella Warb. ex Smith & Wasshausen (1983: 443) , known from lowland limestone forests of Sulawesi, in the creeping habit and small lamina size, but can be easily distinguished by its shorter petioles (0.5–2vs 3−10 cm), male inflorescences comprised of 2−3 monochasial partial inflorescences with caducous bracteoles (vs male inflorescence a monochasium, bracteoles persistent), shorter male flower pedicels (13–16 vs 20–35 mm) and larger male flower tepals (11–13 × 14–15 vs 5–9 × 9–12 mm), and solitary female flowers with 5 tepals (vs female flowers 2-tepalled and usually paired with a single male flower).

Type: — INDONESIA. Sulawesi, Central Sulawesi: Gunung Sidole, Aloo Village , 27 December 2018, E. P. Dayanti ED 12 (holotype BO!; isotype CEB!) .

Perennial, monoecious herb, up to 10 cm tall; stem creeping, rooting at the nodes when in contact with substrate, with microscopic glandular hairs and sparsely hairy with macroscopic hairs to glabrescent on stems. Stem branched, internodes 1–3 cm long, reddish–brownish. Leaves alternate; stipules persistent, ovate to elliptic, ca. 4–5 × 2–3 mm, reddish, glabrous, translucent, midrib abaxially slightly prominent, margin entire, apex acuminate and narrowed into bristle up to ca. 2 mm long; petioles 5–20 mm long, reddish, terete, sparsely hairy; lamina basifixed, ovate to elliptic, 2.5–4.7 × 1.5–2.8 cm, very asymmetric, base cordate, lobes not or sometimes slightly overlapping, apex acuminate, margin serrulate to double serrate to shallowly lobed (up to 20% of lamina width), ciliate, adaxially green-reddish, sometimes irregularly variegated with silvery blotches or silvery on and along the main veins, glabrous to very sparsely hairy between the veins, abaxially pale green, hairy on the veins, venation palmate-pinnate, primary veins 4–6, actinodromous, secondary veins craspedodromous. Inflorescences terminal, protogynous; female flowers solitary, one node basal to the male inflorescence or further separated, peduncle ca. 1.5 mm long, red, glabrous; male inflorescence composed of up to 3 partial inflorescences, each a simple monochasium with 2–3 flowers, peduncle ca. 2.5 mm long, red, glabrous; bracts stipule-like, persistent, ovate, 4–5 × 2–3 mm, translucent, midrib slightly prominent, reddish, glabrous, apex acuminate, and narrowed into bristle ca. 1.5 mm long, bracteoles caducous. Male flowers: pedicels 13– 16 mm long, pink, glabrous; tepals 2, pale pink, broadly ovate to suborbicular, 11–13 × 14–15 mm, abaxially glabrous, margin entire, apex rounded; androecium yellow, stamens 36–40, free filaments 0.3–0.6 mm long, fused at the base, anthers 0.5–1 mm long, dehiscing through unilaterally positioned slits ca. ½ as long as the anthers. Female flowers: pedicels 5–7 mm long, glabrous, reddish; tepals 5, white tinged pink, one smaller, elliptic, 7–9 × 4.5–7.5 mm, the other four larger, broadly ovate, 8–12.5 × 5–12 mm, abaxially glabrous, margin entire, apex rounded; ovary (excluding wings) ellipsoid, 6–8 × 4–5 mm, reddish-greenish, glabrous, locules 3, placentae bilamellate, wings 3, equal, base rounded, apex truncate to subtruncate, widest point 6–8 mm (at the middle to subapically); style up to ca. 2.5 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigma region, stigmatic surface a spirally twisted papillose band, orange. Fruit: peduncles ca. 1.5 mm long; pedicels 7–8 mm long; seed-bearing part ellipsoid, 8–10 × 5–6 mm (excluding the wings), wing shape as for ovary, widest point 7–9 mm. Seeds barrel-shaped, ca. 0.3 mm long.

Distribution: —Endemic to Sidole, Central Sulawesi, Sulawesi, Indonesia.

Habitat: —Montane rainforests, growing terrestrially on steep slopes, in dense shade, at ca. 1700–1900 m elevation.

Etymology: —The species epithet refers to Mount Sidole in Central Sulawesi, where the type material was collected.

Notes: — Begonia sidolensis is an understorey herb that grows on steep slopes. The prostrate-creeping habit is a rare character in Begonia section Petermannia , although some other species with this growth habit are known from Sulawesi and the Moluccas (Sulawesi: B. gemella Warb. ex Sm. & Wassh. ; B. flacca Irmscher (1953a: 486) , B. mattampensis Ardi & D.C. Thomas (2019:23) ; Moluccas: B. manuselaensis Ardhaka & Ardi ( Ardhaka et al. 2016: 61)) .

Apart from similarities to B. gemella (see diagnosis), B. sidolensis also has morphological similarities with B. manuselaensis , a creeping species described from lowland limestone forest from Seram, but B. sidolensis can be easily distinguished by stems and leaves that have a sparse indumentum of simple hairs or are glabrescent (vs a very sparse indumentum of small flattened red scales), shorter petioles (0.5–2 vs 4−7.5 cm), shorter male flower pedicels (1.3−1.6 vs. 4−7 cm) and shorter female flower pedicels (0.5−0.7 vs 1.5−4 cm). Begonia flacca and B. mattampensis are other allied species from Sulawesi, similar in their creeping habit, but B. sidolensis differs in having a much smaller stature. Further, both B. flacca and B. mattampensis are found in lowland limestone karst habitats and have never been reported from high altitudes.

Provisional conservation assessment: —VuD2, Vulnerable. Begonia sidolensis is known from only a single collection from Gunung Sidole. The forest condition at the type locality is good, and currently there are no signs of anthropogenic threats in the montane forest of Gunung Sidole. However, due to the very 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.

Figures

FIGURE 1. Map showing the distribution of Begonia sidolensis (circle) and B. rolandfadlii (square).

FIGURE 2. Begonia sidolensis Dayanti, Ramadanil & Ardi. A. Habit. B. Leaves. C. Stipules. D–E. Male inflorescence. F. Male flowers (front view). G. Female flower (side view). H. Female flower (front view). I. Dry fruit.J. Ovary cross section.All photos from E.P. Dayanti ED 12. Photos: A–I: Eka Dayanti; J: Wisnu Ardi.