Begonia bonthainensis Hemsl. in Bull. Misc. Inform. Kew: 37. 1896

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Begonia Section

  • Petermannia

Description

  • Perennial, monoecious herb, sometimes slightly woody at base, up to ca. 2 m tall; stems erect with microscopic glandular hairs and otherwise glabrous to moderately hairy with multicellular whitish hairs up to ca. 1 mm long. Stem branched, internodes (1.5)2–13.5 cm long, swollen at the nodes, red or brownish red. Leaves alternate; stipules caducuous, 10–35 × 3.5–12 mm, oblong, apex acute, midrib abaxially prominent, projecting up to 10 mm at the apex, margin entire, translucent, reddish to reddish-greenish; petioles (3.5)5–15.5 cm long, adaxially shallowly channelled, glabrous to moderately hairy, reddish to pale green; lamina basifixed, 9–19.5 × 5–13.5 cm, asymmetric, ovate to elliptic, margin dentate or serrate to biserrate, to shallowly lobed (up to ca. 20% of the lamina width), base cordate and lobes not or rarely slightly overlapping, apex acuminate, adaxial surface green, sometimes blue iridescent, glabrous to hairy, abaxially pale green or maroon, glabrous to hairy; primary veins 5–7(–8), actinodromous, secondary veins craspedodromous. Inflorescences: protogynous; female inflorescence positioned one node below the male inflorescences or sometimes solitary, peduncles 1–4.1 cm long, reddish-brownish to red, glabrous to sparsely hairy; male inflorescences dichasially branching, with 5–12 flowers, peduncles 1.9–4.5 cm long, reddish, glabrous to sparsely hairy; bracts ca. 12–20 × 10–12 mm, glabrous, ovate, pale green, thin and papery, caducuous. Male flowers: pedicels 8–15 mm long, white, glabrous; bracteoles 5–7 × 2–4 mm, pale green, translucent, thin and papery, caducuous; tepals 2–4, white, 2 outer tepals 1.8–2.9 × 1.7–2.7 cm, suborbicular to broadly ovate, base slightly cordate, apex rounded, outer surface glabrous, 0−2 inner tepals 0.6−1.6 × 0.2−0.9 cm, oblong, elliptic or obovate; androeci-um yellow, symmetric; stamens ca. 90, filaments ca. 1−2 mm long, fused at the base, anthers up to ca. 1 mm long, obovate, dehiscing through unilaterally positioned slits that are ca. 1/2 as long as the anthers. Female flowers: pedicels 9–17 mm long, green–reddish, glabrous; bracteoles caducuous, 1–1.8 × 1–1.6 mm, broadly ovate, margin entire, apex mucronate, pale green, translucent, thin and papery, glabrous; tepals 5, white, subequal to unequal, ca. 1.8−2.8 × 1−2 cm, elliptic, glabrous, margin entire, apex rounded to obtuse; ovary (excluding wings) 7–13 × 4–9.5 mm, ellipsoid, white or pale green, glabrous, locules 3, placentation axile, placentae bilamellate, wings 3, equal, green, base rounded to cuneate, apex truncate, widest point at the apex 2−8 mm, style up to 9 mm long, basally fused, 3–branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruit: peduncle ca. 1–4 cm long; pedicels 1–2 cm long; seed-bearing part 10–17 × 7–12 mm (excluding the wings), globoid to ellipsoid, glabrous, dehiscent, splitting along the wing attachment, wing shape as in ovary, up to 10–14 mm at the widest point (apically to subapically). Seeds barrel-shaped, ca. 0.3 mm long. (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)

Habitat & Ecology

  • This is a rainforest floor species, often growing at the sides of streams, reported from between c.1700 and 2900 m above sea level.

Conservation

  • Proposed IUCN category: VU D2. The Lompobatang massif is densely populated, and the forests below 1700 m are heavily disturbed. Although the distribution of this species is in the 2000-3000 m range, and hence within a protected area, given pressures on forests in this region this species must be considered as vulnerable. (Hughes, M. An annotated checklist of Southeast Asian Begonia. 2008)
  • Endangered EN B1ab(iii),B2ab(iii). Begonia bonthainensis is only known from several mountains at the Southern tip of South Sulawesi (Mt. Lompobatang, Mt. Bawakaraeng, Mt. Bowonglangit and Mt. Tompobulu) and is locally abundant on Mt. Bawakaraeng. However, none of the localities has a legal status as protected area and potential threats (agriculture, tourism) were observed in the area. This in combination with GeoCAT (Bachman et al., 2011) estimates of an EOO smaller than 5,000 km (112 km2) and an AOO of 24 km2, indicates that this species should be considered Endangered. (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)

Distribution

Endemic to Indonesia, Sulawesi, South Sulawesi: Mt. Lompobatang massif (including Mt. Bawakaraeng), Mt. Bowonglangit and Tompobulu. (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)

Etymology

  • The species epithet refers to Bonthain Peak (Mt. Lompobatang) in South Sulawesi, where the type material was collected. (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)

Notes

  • The original descriptions of B. bonthainensis and B. grandipetala were based on only single collection from type localities on mountains in South Sulawesi which are separated by about 25 km. The protologues indicate qualitative and quantitative characters differentiating the species. According to Hemsley (1896), B. bonthainensis is glabrous to glabrescent, has a dentate to denticulate leaf margin, and male flowers with two tepals. These characters seem distinct from B. grandipetala which has hairy stems, the leaf margin is serrate to biserrate, and shallowly lobed, and the male flowers have four tepals (Irmscher, 1913).
    Hughes et al. (2018) included both species in their photo guidebook and noted that Begonia bonthainensis differs from B. grandipetala by its slightly smaller male flowers with two tepals, and the identification key in Thomas et al. (2011) uses leaf margin and male flower characters to differentiate the two species. However, the type material also shows conspicuous similarities such as male flowers in dichasially branching inflorescences with well-developed internodes, female inflorescences with relatively long peduncles and long pedicels, and very similar fruit shapes, which clearly indicates a close relationship. During expeditions to the Mt. Lompobatang massif including Mt. Bawakaraeng in 2009 and 2018, considerable variation of the indumentum of the stem and petioles (glabrous to moderately hairy), leaf margin serration and leaf-lobing, and number of male flowers tepals (two to four) were observed within and between populations (e.g. Ardi 362 [BO, FIPIA, SING]; DCT 09-69 [E]; EAW 9164 [BO]). The observed variation on Mt. Bawakaraeng in combination with the similarity of crucial generative characters (inflorescence, fruits) of the type specimens, and variation observed in additional specimens examined (see above) from localities connecting the two type localities, lets us conclude that the differences in the type material are at the individual or population level in a continuous morphospace. Consequently, we propose to put the more recent name, Begonia grandipetala, in synonymy. (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)

Molecular Systematics

  • see Thomas et al., 2012 (Thomas, D.C., Hughes, M., Phutthai, T., Ardi, W.H., Rajbhandary, S., Rubite, R., Twyford, A.D. & Richardson, J.E. 2012: West to east dispersal and subsequent rapid diversification of the mega-diverse genus Begonia (Begoniaceae) in the Malesian archipelago. – Journal of Biogeography 39: 98-113)
  • Genbank

Specimens

  • Bonthain Peak, 12 Dec. 1976, W. Meijer 11035 (E); Bonthain Peak, 12 Dec. 1976, W. Meijer 11036 (BO, L); Bonthain Peak, 18 May 1921, H.A.B. Bunnemeijer 11067 (BO); Lombasang, 26 May 1921, H.A.B. Bunnemeijer 11729 (BO); Bonthain Peak, 10 June 1921, H.A.B. Bunnemeijer 12030 (BO); Bonthain Peak, 11 June 1921, H.A.B. Bunnemeijer 12046 (BO); Gunung Bawakaraeng, South Sulawesi, 12 Apr. 2009, D.C. Thomas & W.H. Ardi, DCT 09-63 (BO, E, L); South Sulawesi, Malino, Gunung Bawakaraeng, 12 Apr. 2009, D.C. Thomas & W.H. Ardi, DCT 09-69 (BO, E, L); Gowa District, Tompobulu, Cikoro village, 29 Oct. 2010, Agus Suyadi et al. EAW 9164 (BO, E); South Sulawesi, Malino, Lembana Waterfall, 14 Apr. 2018, W.H. Ardi WI 362 (BO, FIPIA, SING). (Ardi, W.H. & Thomas, D.C. 2019. A new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia, and an augmented description of Begonia bonthainensis in Reinwardtia 18(1): 19-26.)