Begonia mabberleyana D.C.Thomas & Ardi, Gard. Bull. Singapore 71(Suppl. 2): 218. 2019

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Begonia Section

  • Petermannia

Diagnosis

  • The many-flowered male inflorescences, male inflorescence architecture, small male flowers (tepals 3–7 × 3–7 mm), and variable male tepal coloration indicate a close relationship of Begonia mabberleyana with the morphologically similar Begonia stevei M.Hughes. Begonia mabberleyana can be differentiated by its shorter petioles (0.1–1 cm vs 1–4 cm); leaves which are coarsely toothed, serrate or shallowly lobed in the distal part only (vs lamina irregularly incised); pinnate lamina venation (vs venation palmate-pinnate); minute and caducous bracteoles of the male inflorescences (vs bracteoles well-developed and semi-persistent); and solitary female flowers and fruits, fruit pedicels that are up to 7 mm long and borne on strongly compressed branches to c. 1 mm long (vs female flowers and fruits in pairs, pedicels to 12 mm long, peduncles to 8 mm long). (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Description

  • Perennial, monoecious herb, up to c. 80 cm tall; stems erect, with microscopic glandular hairs and a sparse indumentum of multicellular, bristly hairs to c. 0.5 mm long. Stem branched, internodes 2–8 cm long, greenish or brownish-reddish. Leaves alternate; stipules caducous, 6–9 × 3–5 mm, ovate to elliptic, acuminate, apex narrowed into bristle up to 2 mm long, greenish, glabrous; petioles 0.1–1 cm long, greenish or reddish, sparsely hairy; lamina basifixed, 7–15 × 3.3–10 cm, asymmetric, obovate, base asymmetrically cuneate, convex or cordate (lobes not overlapping), apex acute, margin coarsely dentate to serrate and sometimes shallowly lobed in the distal lamina half, the teeth not bristle-pointed, adaxial surface green with red to green veins, sometimes variegated with white dots between the veins, glabrous or sometimes sparsely bristly between and on the veins, abaxial surface pale green and with red veins, sparsely hairy on the veins; venation pinnate, with 3–5 secondary veins on each side, these craspedodromus. Inflorescences protogynous; female flowers solitary, usually one node basal to male inflorescences or sometimes separate, peduncles to c. 1 mm long; male inflorescences racemose-cymose, composed of several cymose partial inflorescences each branching dichasially in the basal part and monochasially in the more distal part, or purely monochasially, each with several to numerous flowers; peduncles to 3 cm long; bracts minute, caducous. Male flowers: pedicels 2–5 mm long, greenish, whitish-greenish, or white tinged with pink, glabrous; tepals 2, white, whitish-greenish, white tinged with pink or pinkish, ovate to suborbicular, 3–7 × 3–7 mm, margin entire, apex rounded, glabrous; androecium of c. 23–27 stamens, yellow, filaments c. 0.5 mm long, slightly fused at the very base, anthers to c. 1 mm long, oblong or narrowly obovate, dehiscing through unilaterally positioned slits c. 1/2 as long as the anthers. Female flowers: pedicels 3–5 mm long, greenish, glabrous; tepals 5, whitish-greenish, subequal, 3–7 × 3–5 mm, ovate to elliptic, glabrous; ovary ellipsoid, 6.5–7 × 3–5 mm (excluding the wings), pale green, glabrous, locules 3, placentation axile, placentae bilamellate, wings 3, equal, base rounded, apex subtruncate to truncate, style c. 4 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, yellowish to orange. Fruits: pedicels 6–7 mm long, curved downwards at apex; seed-bearing part ellipsoid, 8–12 × 4–7 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 to subapically). Seeds barrel-shaped, c. 0.2–0.3 mm long. (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Habitat

  • Growing terrestrially or lithophytically in lowland rain forest, along small streams and rivers, on limestone soils or directly on limestone rock, in dense to partial shade, at c. 50–300 m elevation. (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Conservation

  • Critically Endangered CR B1ab(iii),B2ab(iii). Begonia mabberleyana is known from two localities of lowland rain forest on limestone, neither of which is in a legally protected area. About 30 individuals were observed in the Lamala District population, but this locality is in disturbed forest surrounded by agricultural land. The other locality is only known from two collections by Coode from 1989 (Coode 5952, 6013). Exploration of several localities in lowland forest in the Banggai Regency including areas north of Batui, presumably close to where the Coode specimens were collected, did not result in any additional collections of this species. The small extent of occurrence (EOO) and area of occupancy (AOO), in combination with the fragmented distribution, observed threats, and generally poor state and ongoing reduction of lowland forest habitats in the area (see Cannon et al., 2007), indicate a Critically Endangered status. (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Distribution (General)

  • Endemic to Central Sulawesi, Sulawesi, Indonesia. Known from only two localities in Banggai Regency: near Sirom in Lamala District and inland from Batui in Batui District. (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)A
A. Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019

Etymology

  • This species is named in honour of David Mabberley; a prominent tropical botanist and determined champion of the Flora Malesiana project (floramalesiana.org). (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Notes

  • Begonia mabberleyana shows considerable tepal colour variation. Within the Lamala population, individuals with male flowers with either greenish, white, white tinged with pink, or pink tepals were observed. Such wide range of tepal coloration is rare in Sulawesi Begonia, but similar to the closely related Begonia stevei. Individuals derived from a single seed collection of Begonia stevei were reported to have a male tepal colour range from pale green to coral orange-pink (Hughes, 2006). (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)

Specimens

  • INDONESIA: Central Sulawesi: Luwuk area, inland from Batui and Seseba on Batui R., at Sinsing camp, c. 1°09′S, 122°31′E, 70–100 m, 15 Oct 1989, Coode 5952 (K); Luwuk area, inland from Batui and Seseba on Batui R., at Totop camp, 2 hrs upriver from Sinsing, c. 1°09′S, 122°31′E, 150 m, 19 Oct 1989, Coode 6013 (E, K, L); Banggai, west of Boloak village, May 2016, Trethowan 286 (BO); Banggai, c. 2 hour hike west from Boloak village, 0°51′51.1″S, 123°16′50.8″E, 278 m, Oct 2016, Trethowan 1032 (BO); ibid., Oct 2016, Trethowan 1033 (BO). (Thomas, D.C. & Ardi, W.H., Begonia mabberleyana (Begoniaceae), a new species from Central Sulawesi, Indonesia in Gardens' Bulletin Singapore, Suppl. 2, 71: 217-223. 2019)