Begonia sangkulirangensis Ardi, Girm. & Randi, 2022

Randi, Agusti, Ardi, Wisnu H., Girmansyah, Deden, Sitepu, Bina Swasta & Hughes, Mark, 2022, Three new species, one new record and an updated checklist of Begonia (Begoniaceae) from Kalimantan, Indonesia, Phytotaxa 533 (1), pp. 62-72 : 67-69

Begonia sangkulirangensis Ardi, Girm. & Randi , sp. nov. B. sect. Petermannia ( Fig. 3 ).

Type:— INDONESIA, East Kalimantan Province, Karst Sangkulirang, Bengalon, Goa Tewet Trail , 1°3’47.9”N, 117°16’11.4”E, ca. 80 m elev. (cultivated at Bogor Botanic Garden from material collected in the wild (Hughes M., Girmansyah D., Yeats H. & Ardiyani M. EKBOE138 ), 4 December 2019, Wisnu H. Ardi WI 684 (holotype BO!).

Diagnosis:— The erect habit and peltate leaves of B. sangkulirangensis are similar to B. nothobaramensis Joffre (2015: 35) from Brunei but it can be easily distinguished by its shorter (50‒60 cm vs. 100 cm) habit, smaller (7–12 × 3.5–5.5 cm vs. 9.5–18 × 5–9 cm) lamina, more (45‒55 vs. ca. 36) stamens, female inflorescence consistently with a single (vs. two) flower on a shorter (10–13 mm vs. 17‒20 mm) pedicel, ovary wing shape cuneate (vs. rounded) at the base and apex. Begonia sangkulirangensis also differs from both B. baramensis and B. nothobaramensis in having a thicker and more succulent leaf lamina.

An erect herb, up to ca. 50 cm tall. Stem branched, nearly glabrous except for moderate microscopic glandular hairs, reddish-brown, internodes 2–9 cm apart. Stipules caducous, glabrous, elliptic, 6–8 × 2–4 mm, midrib prominent, margin entire, translucent, apex narrowed into bristle up to 1.5 mm long; whitish-greenish. Leaves simple, alternate, glabrous; petioles 2–5 cm long, concolourous with the stem, terete; lamina peltate, coriaceous, elliptic, 7–12 × 3.5–5.5 cm, asymmetric, apex acuminate, margin subentire, serrate from the middle part upward to the apex, adaxial surface dark green with brownish veins, abaxial surface pale green, veins reddish to brownish; venation palmate-pinnate, primary veins 5–6, actinodromous, secondary veins craspedodromous.Inflorescence protogynous; female inflorescence solitary, one node basal to male inflorescence or further separated, peduncle 3−5 mm long, reddish-green, glabrous, bracteoles minute, hairlike, persistent; upper distal that bearing male inflorescence paniculate, composed of up to 4 simple monochasium with 4–7 flowers, peduncle 5–8 mm long, glabrous; bracts stipule-like, persistent, ovate, ca. 4 × 1.5 mm, translucent, midrib slightly prominent, pale green, glabrous, apex acuminate and narrowed into bristle ca. 1 mm long; bracteoles persistent, minute. Staminate flower pedicel up to 7.5 mm long, whitish-green, glabrous; tepals 2, broadly ovate, 4–6 × 5–7 mm, greenish-red or dull cream, glabrous, margin entire, apex rounded; androecium symmetric with 48–55 yellow stamens, filaments up to ca. 1 mm long, fused at the base, anthers ca. 0.5 mm long, dehiscing through unilaterally positioned slits ca. ½ as long as the anthers. Pistillate flowers: pedicels 10–13 mm long, pale green, glabrous; ovary 3-locular, cylindrical, 16−18 × 2−3 mm (wings excluded), pale green, glabrous, placentae bilamellate, wings 3, subequal, base cuneate to rounded, apex subcuneate, widest point up to 7 mm (1 / 3 from the apex); tepals 5, glabrous, white tinged with pink and green, unequal, one smaller elliptic, 5−6 × 2−3 mm, the four larger ovate, 8–9 × 4.5–6 mm, margin entire, apex rounded; style ca. 4.5 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruit peduncle up to 5 mm long; pedicels up to 15 mm long, pendulous and recurved; seed-bearing part cylindrical, 16−19 × 3−4 mm (wings excluded), wing shape as for ovary, widest point up to ca. 8 mm. Seeds barrel-shaped, 0.2–0.3 mm long.

Distribution: —Endemic to Borneo, so far only known from the type locality in the Sangkulirang-Mangkalihat Limestone Karst Ecosystem, East Kalimantan Province, Indonesia.

Habitat:— This species was found on a limestone cliff in a shallow cave in deep shade beneath scrubby karst vegetation. It was growing in thin dusty soil on a slightly damp mossy rock.

Etymology:— The epithet refers to the name of Sangkulirang, the Limestone Karst Mountain Ecosystem where this species was found.

Provisional Conservation Status:— Vulnerable (VU, D2). This species is only known from single collection from the Sangkulirang Mangkalihat Limestone Karst Ecosystem. The area does not yet have legal protected status, and there are clear signs of anthropogenic disturbance (oil palm plantations and mining) around the karst formations. As a karst micro-endemic it therefore is ‘prone to the effects of human activities or stochastic events within a very short time period in an uncertain future’ ( IUCN Standards and Petitions Subcommittee 2019). An ex-situ initiative has been started with plants being cultivated at Kebun Raya Bogor (Bogor Botanic Garden).

Notes: —There are four other caulescent species in B. sect. Petermannia in Borneo with conspicuously peltate leaves: B. amphioxus Sands (1990: 81) , B. baramensis Merrill (1928: 529) B. layang-layang Kiew (2001b: 272) and B. nothobaramensis Joffre (2015: 35) . Begonia sangkulirangensis is closest to B. nothobaramensis as discussed in the diagnosis above, and B. baramensis is a much larger plant, reaching up to 3 m tall ( Kiew et al. 2015). Begonia amphioxus and B. layang-layang do not appear to be closely allied, both differing most obviously in their leaves which are acute at the base and tip.

Figures

FIGURE 3. Begonia sangkulirangensis Ardi, Girm. & Randi. A. Habit; B. Lamina abaxial surface; C. Stipule; D. Male inflorescence; E. Female and male inflorescence; F. Male flowers, G. Female flower; H. Fruit; I. Ovary cross section. Scale bars:A: 5 cm, B: 1 cm, C: 1 mm, D: 5 cm, E: 10 mm, F–G: 5 mm, H: 10 mm, I: 1 mm. Photo A: Mark Hughes; B‒I: Wisnu H. Ardi, from cultivated specimen WI 684.