Begonia cuneatifolia Irmsch. [§ Petermannia

Ardi, W. H. & Thomas, D. C., 2022, SYNOPSIS OF BEGONIA (BEGONIACEAE) FROM THE NORTHERN ARM OF SULAWESI AND SANGIHE ISLAND, INDONESIA, INCLUDING THREE NEW SPECIES, Edinburgh Journal of Botany 79 (405), pp. 1-50 : 15-17

5. Begonia cuneatifolia Irmsch. [§ Petermannia ], Bot. Jahrb. Syst. 50: 370 (1913).

– Type

: Indonesia, Sulawesi, Minahasa, Tomohon , 19 iv 1894, K.F. & P.B. Sarasin 494 (holotype B [B10238206], isotype K [K000761121]). Figure 4 .

Perennial, small monoecious herb, erect, up to c. 35 cm tall. Stem mostly branched in the basal part; internodes 2.5–7 cm long, slightly swollen at the nodes, brownish-reddish, sparse to moderately densely covered with strigose hairs. Leaves basifixed, alternate; stipules caducous, c.5.5–10 × 2 mm, elliptic, with an abaxially slightly prominent midrib, apex narrowed into bristle projecting up to 1 mm, margin entire, creamy, translucent, abaxially sparsely hairy; petioles 0.5–2.5 cm long, terete, concolorous with the stem, moderately to densely covered with strigose hairs; lamina 7–12 × 1.5–3 cm, asymmetrical, elliptic, base strongly oblique, lobes not or just slightly overlapping, apex acuminate, margin entire or serrulate in the distal two-thirds of the lamina, adaxial surface green, with reddish veins and margin, glabrous, abaxial surface maroon, hairy on the veins only; venation pinnate, secondary veins craspedodromous. Inflorescences protogynous, female inflorescences basal to male or solitary; female inflorescences 1- or 2-flowered, or frequently a male flower developed between the two female flowers (a dichasium), peduncles 1–2 mm long, green reddish, hairy; male inflorescences racemose-cymose (a thyrse), with up to 7 partial inflorescences, branching dichasially (the basal partial inflorescences), dichasially-monochasially, or monochasially (the distal partial inflorescences), with up to 8 flowers, peduncle of partial inflorescence 1.5–3 mm long, bracts stipule-like, c.7 × 2.5 mm, elliptic, pale green, translucent, midrib slightly prominent, glabrescent, apex narrowed into bristle projecting up to 1 mm, caducous. Male flowers: pedicels 8–15 mm long, white-greenish or white-pinkish, sparsely hairy; tepals 2, white, 10–13 × 10–11 mm, ovate to elliptic, base slightly cordate and truncate when the flowers open, apex rounded, outer surface sparsely hairy in the basal part; androecium of c.40 stamens, yellow, filaments c. 0.5–1 mm long, slightly fused at the very base, anthers up to c. 1 mm long, oblong to narrowly obovate, dehiscing through unilaterally positioned slits that are c.1/2 as long as the anthers. Female flowers: pedicels 3–4 mm long, green-reddish, sparsely hairy; tepals 5, white, subequal, 8–10 × 4–6 mm, elliptic, outer surface glabrous; ovary (excluding wings) 7–9 × 3–5 mm, ellipsoid, pale green-reddish, glabrous, locules 3, placentation axile, placentae bilamellate, wings 3, equal, reddish, rounded to slightly cuneate at the base, truncate at the apex or sometimes rounded, wing margin entire to serrulate, up to 5 mm at the widest point (apically or subapically); style c. 3.5 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruits: peduncles c. 5 mm long; pedicels 3–4.5 mm long; seed-bearing part ellipsoid, 11–13 × 4.5–6.5 mm (excluding the wings), glabrous, dehiscent, splitting along the wing attachment, wing shape as for ovary, up to 10 mm at the widest point (apically). Seeds barrel-shaped, c. 0.2 mm long.

Distribution. Indonesia: endemic to Sulawesi, Central, North and Gorontalo Provinces, Toli-toli, Sigi (Gunung Gawalise) (see Figure 2 ).

Habitat. Disturbed lowland to upland forest at 300–1300 m elevation.

Proposed IUCN conservation category. Endangered (EN), B2ab(iii). This species’ distribution includes lowland forest habitats on the northern arm of Sulawesi (Toli-toli and Tomohon) and also upland forest on Gunung Gawalise. Recently, small populations of Begonia cuneatifolia were observed in the unprotected area of Gunung Gawalise and the Malangga waterfall (Toli-toli). The species is known from only a few collections, and most collection localities were secondary forests in close proximity to settlements and agricultural land and showed signs of severe anthropogenic disturbance. Given the patchy and relatively small distribution (EOO, 21381 km 2; AOO, 12 km 2) and the poor state and pressures of lowland rain forest habitats on Sulawesi ( Cannon et al., 2007), an Endangered status is appropriate ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimens examined. INDONESIA. Sulawesi. Northern arm of Sulawesi. Central North Sulawesi: Gorontalo, Gunung Boliohutu , 24 iv 2002, M. Mendum et al. 189 (E, K) . Eastern North Sulawesi: Minahasa , Roeroekan , 1933, C.A. Wisse s.n ( WAG) .

Central Sulawesi Province: Tolitoli regency, Malangga district , 18 i 2019, Zulfadly ZF 43 ( BO) ; Gunung Gawalise, Donggala , 4 x 2020, M. Fajri Ramadhan 1724 ( CEB) .

Begonia cuneatifolia is a distinctive species among the members of Begonia sect. Petermannia in Sulawesi. It can be easily recognised by its short petiole, long and narrow leaves with pinnate venation, and short male and female inflorescence peduncles. At first sight, it is vegetatively similar to many species from Borneo, such as Begonia bruneiana Sands , B. jugamensis S.Julia & Kiew , B. labiensis (Sands) S.Julia and B. lambirensis Kiew & S.Julia, but it can be easily distinguished by its terminal inflorescence, in contrast to the axillary inflorescences of those Bornean species.

Figures

Figure 2. Distribution maps of Begonia species occurring on the northern arm of Sulawesi. Distribution points are from georeferenced collections from major herbarium collections (B, BO, E, K, KRB, L, SING), the Begonia Resource Centre (Hughes et al., 2015–) and the Sulawesi Begonia Data Portal (Thomas et al., 2013, continuously updated).

Figure 4. Begonia cuneatifolia. A, Habit; B, lamina; C, male inflorescence; D, male flower (front view); E, female inflorescence; F, female flower (front view). A–F from Zulfadly ZF43. Photographs: Zulfadly.