Begonia willemii Ardi, Girm. & D.C.Thomas, Taiwania 66(3): 374. 2021

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Begonia Section

  • Petermannia

Diagnosis

  • The creeping growth habit, the relatively small leaf laminas, and the monochasially branching male inflorescences are similar to Begonia gemella Warb. Ex L.B.Sm. & Wassh. (1983) from Minahasa, Sulawesi, but B. willemii can be distinguished by a smaller leaf lamina (3–8 × 2.5–6 cm versus 5–9.5 × 4.5–8 cm for B. gemella) with a sparse indumentum of red bristle hairs between the veins on the adaxial surface (versus glabrous), male flowers in simple monochasial cymes (versus thyrses composed of up to 3 monochasial cymes), longer male flower pedicels (2–4 cm versus 1.5–1.8 cm long), fewer stamens (c. 19‒23 versus ca. 75–77), and female flowers consistently with two tepals (versus five tepals). (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)

Description

  • Perennial, monoecious evergreen? herb, to c. 1 m long. Stem creeping, internodes 1–5 cm long, reddishgreenish, slightly swollen at the nodes, brownish-reddish, glabrous except for microscopical glandular hairs. Leaves basifixed, alternate; stipules persistent, 4–6 × 2.7–4 mm, anisophyllus, ovate to elliptic, with an abaxially slightly prominent midrib, apex mucronate projecting up to 2 mm, margin entire, cream-coloured, glabrous; petioles 3–13 cm long, terete, stem, reddish-greenish, glabrous; lamina 3–8 × 2.5–6 cm, asymmetric, broadly ovate to ovate, base cordate and lobes sometimes overlapping, apex acuminate, margin serrate-biserrate, adaxial surface green or green-purplish, with a sparse indumentum of red bristles between the veins, abaxially pale green, sparsely hairy on the veins; venation palmate-pinnate, primary veins 5–6, actinodromous, secondary veins craspedodromous. Inflorescences protogynous, female flower usually in a mixed inflorescence with 1 or rarely 2 male flowers, peduncles c. 0.5–2 cm long; male flowers in mixed inflorescences with a single female flower or in purely male monochasia with short internodes and up to 6 flowers, peduncle 1.5–3 cm long, bracts persistent, stipule-like, 3–5 × 2–3 mm, ovate, reddish, translucent, midrib slightly prominent, a short bristle projecting at the apex, bracteoles persistent, c. 3 × 2 mm, ovate. Male flowers pedicels 2–4 cm long, white-pinkish, glabrous; tepals 2, white to white tinged with pink, 5–10 × 7–12 mm, broadly ovate, base slightly cordate, apex rounded, outer surface glabrous; androecium of c. 19‒23 stamens, yellow, filaments up to c. 1 mm long, slightly fused at the very base, anthers c. 0.5‒1 mm long, oblong to obovate, dehiscing through unilaterally positioned slits that are c. ½ as long as the anthers. Female flowers pedicels 7–15 mm long, reddish-greenish, glabrous; tepals 2, white, or white tinged with pink, 7–10 × 9–14 mm, broadly ovate, outer surface glabrous; ovary (excluding wings) 4–9 × 3–6 mm, ellipsoid, pale green, locules 3, placentation axile, placentae bilamellate, wings 3, equal, pale green, base rounded, apex truncate to rounded, sometimes beaked, 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 1.1–3 cm long; pedicels 5–15 mm long, slightly recurved; seed-bearing part cylindrical to ellipsoid, 6–10 × 4–7 mm (excluding the wings), glabrous, dehiscent, splitting along the wing attachment, wing shape as for ovary, up to 7 mm at the widest point (apically or subapically). Seeds ellipsoid to obovoid, 0.35–0.38 mm long, collar cells more than a half of seed length. (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)

Habitat

  • Lowland limestone karst forest, disturbed forest, growing vertically on limestone rock, or terrestrially on the base of limestone cliffs, in half to full shade, at 10 to 50 m elevation. (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)

Conservation

  • Begonia willemii is endemic to Sulawesi, where it has a patchy but relatively wide distribution (EOO: 22534 km2, AOO: 32 km2) closely associated with lowland limestone forest habitats. However, its range does not include any legally protected areas. Lowland forests have been declining on Sulawesi due to anthropogenic pressures, and lowland limestone forests are among the most threatened forest types on the island (Cannon et al., 2007). Consequently, we assess this species as Near Threatened (NT) (IUCN, 2019). (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)

Distribution

Indonesia. Endemic to Sulawesi (Fig. 2), Gorontalo Province (Gorontalo Regency) and Central Sulawesi Province (Luwuk Banggai and Toli-toli Regencies).

[See images for distribution map]

Notes

  • Apart from the similarity to Begonia gemella Warb. ex L.B.Sm. & Wassh. as elaborated on in the diagnosis above, B. willemii is also similar to B. sidolensis Dayanti, Ramadanil & Ardi and B. manuselaensis Ardhaka & Ardi, both of which also have a growth habit characterised by a creeping stem and lax internodes, small leaf laminas and single female flowers. A detailed comparison of B. willemii, B. sidolensis and B. manuselaensis is presented in Table 1. (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)

Specimens

  • INDONESIA. Sulawesi. Gorontalo: Gunung Boliohutu, 22 Apr 2002, M. Mendum et al. 155 (BO, E); Gorontalo Regency, Boliohutu, 14 Mar. 2008, Kate Amstrong 364 (E); Central Sulawesi: Buol, 15 Aug. 1894, Sarasin 683 (K); Buol, 15 Aug. 1894, Sarasin 689 (B); Luwuk Banggai regency, Hanga-hanga waterfall, 08 Feb. 2019, Wisnu Ardi et al. WI 413 (BO, SING, KRB); Luwuk Banggai regency, Batu tikar waterfall, 09 Feb. 2019, Wisnu Ardi et al. WI 415 (BO, SING, KRB); Luwuk Banggai regency, Batu tikar waterfall, 09 Feb. 2019, Wisnu Ardi et al. WI 416 (BO, SING, KRB); Luwuk Banggai regency, Salodik, 11 Feb. 2019, Wisnu Ardi et al. WI 422 (BO, SING); Luwuk Banggai regency, Bunta, 14 Feb. 2019, Wisnu Ardi et al. WI 428 (BO, SING, KRB); Toli-toli regency, 16 Jan. 2019, Zulfadli ZF 42 (BO, SING); Luwuk Banggai regency, Batui river, 17 Oct. 1989, M. Coode 5985 (E, L). (Ardi, W.H., Girmansyah, D., Zulfadli & Thomas, D.C. 2021: Begonia willemii, a new species of Begonia from Sulawesi, Indonesia. – Taiwania 66(3): 374-377)