Begonia strachwitzii Warb. ex 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 : 44-46

19. Begonia strachwitzii Warb. ex Irmsch. [§ Petermannia ], Bot. Jahrb. Syst. 50: 357 (1913).

– Type: Indonesia, Sulawesi, Minahasa, Bojong , O. Warburg 15192 (holotype B [B100238025], isotype B [B100238026]). Figure 14 .

Perennial, monoecious herb, erect, up to c. 30 cm tall. Stem branched; internodes 2.5–7.5 cm long, slightly swollen at the nodes, brownish-reddish, densely hairy. Leaves basifixed, alternate; stipules semi-persistent, 6.5–8 × 3–4 mm, ovate to oblong, with an abaxially slightly prominent midrib, apex narrowed into bristle projecting up to 3 mm, margin entire and keeled, pale green, translucent at the margin, abaxially hairy; petioles 3–9.5 cm long, terete, not channelled, concolorous with the stem, densely hirsute; lamina 7.5–12 × 4.5–9 cm, asymmetrical, ovate to suborbicular, base cordate and lobes not or just slightly overlapping, apex acuminate, margin dentate-denticulate, adaxial surface green, with red veins, glabrous, abaxial pale green, glabrous; venation palmate-pinnate, primary veins 6–8, actinodromous, secondary veins craspedodromous. Inflorescences protogynous; female inflorescences basal to male, 2-flowered, peduncles 5–10 mm long; male inflorescence a thyrse, with up to 5 (or 6) cymose partial inflorescences, each branching dichasially or dichasially at the base and monochasially in the distal part, with up to 10 flowers, peduncle of partial inflorescence c. 15 mm long, bracts caducous. Male flowers: pedicels 10–15 mm long, white-pinkish, glabrous; tepals 2, white to white tinged with pink, 7–11.5 × 6–11.5 mm, ovate to broadly ovate, base slightly cordate, apex rounded, outer surface glabrous; androecium of c.20–25 stamens, yellow, filaments up to c. 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 7–12 cm long, pale green, glabrous; tepals 5, white, subequal, 9–12 × 3–5 mm, ovate to elliptic, outer surface hairy; ovary (excluding wings) c.6–8 × 3 mm, cylindrical, pale green with red longitudinal lines along the middle of the ovary and along the wing attachment, glabrous, locules 3, placentation axile, placentae bilamellate, wings 3, equal, pale green, base mostly cuneate, sometimes rounded, apex truncate, up to 4 mm at the widest point (apically or subapically); style c. 2.5 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruits: peduncles c. 5–10 mm long; pedicels 5–15 mm long, recurved; seed-bearing part ellipsoid, 10–13 × 3–4.5 mm (excluding the wings), light green with red longitudinal lines along the middle part and the wing attachment, glabrous, dehiscent, splitting along the wing attachment, wing shape as for ovary, up to 7 mm at the widest point (apically or subapically). Seeds barrel-shaped, c. 0.2 mm long.

Distribution. Indonesia: endemic to Sulawesi, North Sulawesi Province (eastern and central North biogeographical regions), Mount Lolombulan and Bolaang Mongondow (see Figure 2 ).

Habitat. Growing terrestrially on the humus-covered slopes of secondary lowland to hill forest, in full shade, at 190–800 m elevation.

Proposed IUCN conservation category. Vulnerable (VU D2). Begonia strachwitzii is known from a few collections from the northern arm of Sulawesi (Gunung Lolombulan and Tapakolintang). The forest at the type locality and the wider area around it is in relatively fair condition. There are, however, signs of anthropogenic threats, such as clove plantations, in the lower montane forest of Gunung Lolombulan. Because of the very restricted range (EOO, 54 km 2; AOO, 8 km 2), the limited number of observed populations, and the poor state of and pressures on lowland rain forest habitats on Sulawesi, the status of Vulnerable seems warranted ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimens examined. INDONESIA. Sulawesi. Northern arm of Sulawesi. Eastern North Sulawesi: Minahasa , Bojong , s.d., O. Warburg 15191 ( B) ; Mongondow Selatan, Tapakolintang , 29 x 2016, S. Barber et al BAAK 6 ( BO, E) ; Mount Lolombulan, above Boyong atas, 24 ii 2008, J. Kinho & A.D. Poulsen 170 ( BO, E) ; Desa Boyong , 4 ii 2019, W.H. Ardi WI407 ( BO, SING) .

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 14. Begonia strachwitzii. A, Habit (WI407); B, habit (BAAK 6); C, stipule; D, hairy petiole; E, male inflorescence; F, male flower (front view); G, female flower; H, infructescence; I, ovary (cross-section of middle part). A, C–F, H and I from W.H. Ardi WI407; B and G from S. Barber et al. BAAK6. Photographs: A, C–F, H and I, W.H. Ardi; B and G, S. Barber.