Begonia mendumiae M.Hughes in Edinburgh J. Bot. 63(2-3): 196. 2006

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Content

Begonia Section

  • Petermannia

Diagnosis

  • A Begonia siccacaudata J.Door. foliis magis pilosis et magis asymmetricis differt. - Type: Sulawesi, Gorontalo, Gunung Ali, growing on almost vertical rock face in heavy shade, 200 m, 28 iv 2002, M. Mendum, H.J. Atkins,M.F. Newman, Hendrian & A. Sofyan 240 (holo E). (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)

Description

  • Creeping pubescent herb to c.20 cm high. Stem rhizomatous, c.7 mm across with scattered hairs; internodes 5-10 mm.

    Stipules broadly lanceolate, 10 × 8 mm with a filiform extension at the tip, fimbriate on the keel. Petioles 5-10 cm long with scattered hairs, pink. Leaves very asymmetric, up to 9 cm long from base to tip, up to 6 cm wide, midrib 4-5.5 cm, ovate with an acute tip, venation palmate-pinnate, scattered with pinkish red hairs, margin shallowly sinuate-dentate with a fringe of short hairs, cordate at the base, lobes sometimes overlapping, deep green in the centre and around the margin with darker mottling on the veins, a paler band running inside the margin.

    Inflorescence bisexual, terminal, protogynous; bracts ovate to sub-orbicular, c.4 mm long.

    Male flowers borne distally to the female in a monochasial cyme with up to three sub-umbellate clusters (actually very compressed cymes) of 6-8 flowers, subtended by 2 bracts with no others visible; tepals 2, suborbicular, c.12 × 12 mm, base cordate becoming truncate at maturity, pale dusky pink; stamens 35, orange, anthers c.0.75 mm long, dehiscing through slits more than half as long as the anther, filaments c.three times as long, slightly fused at the base.

    Female flowers borne singly at the base of the inflorescence, subtended by two bracteoles c.5 mm from the base of the ovary; pedicel c.1.5 cm long; tepals 5, sub-equal, broadly ovate-lanceolate, slightly fimbriate, dusky pink, outer pair 15 × 12 mm, inner three 14 × 6-11 mm; styles 3, twice spirally twisted, orange, deciduous; ovary 13 × 12 mm with 3 equal wings, deep dull-red, truncate across the apex, with scattered hairs, placentation axillary, placentae bifid, wings rounded at the base and acute at the tip.

    Fruit c.13 × 12 mm, drying pale brown, dehiscent; capsule oval, 8 × 5 mm. Seeds barrel shaped, c.0.3 mm long, collar cells c.2/3 the length of the seed. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)

Habitat

  • The species was observed growing on various substrates (soil, limestone rock, and other rock types) in secondary lowland to hill forest and even in a forest remnant in a cocoa plantation, in full to half shade, at 20–600 m elevation. (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 J. Bot. 79(Begonia special issue, article 405): 1-50. http://doi.org/10.24823/EJB.2022.405)

Conservation

  • Proposed IUCN category: VU D2. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)
  • Near Threatened (NT). Begonia mendumiae is endemic to Sulawesi and relatively widespread on the island (EOO, 45,962 km2; AOO, 32 km2), mostly occurring in disturbed lowland forest or limestone forest habitats. However, its known range does not include any legally protected areas in Sulawesi. Consequently, we assess this species as Near Threatened (IUCN Standards and Petitions Subcommittee, 2019). (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 J. Bot. 79(Begonia special issue, article 405): 1-50. http://doi.org/10.24823/EJB.2022.405)

Distribution

Indonesia: endemic to Sulawesi, Gorontalo and Central Sulawesi Provinces (Donggala, Poso)

See images for distribution map. (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 J. Bot. 79(Begonia special issue, article 405): 1-50. http://doi.org/10.24823/EJB.2022.405)

Etymology

  • It is named in memory of the late collector, Mary Mendum. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)A
A. Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.

Notes

  • I have diagnosed this species against Begonia siccacaudata as it is the only other Sulawesi species with anything like a similar habit, but it differs greatly in terms of inflorescence structure. Begonia mendumae has a sub-umbellate male inflorescence, whilst B. siccacaudata bears its male flowers in a comparatively lax thyrse. (Four new species of Begonia (Begoniaceae) from Sulawesi. Edinburgh J. Bot. 63.: 191-199. 2006.)
  • Based on observations in the field, Begonia mendumiae is morphologically highly variable, particularly regarding the indumentum density, leaf size and coloration, and ovary shape both among individuals in populations and among different populations. However, most generative characters are more stable, allowing clear identification of the species. Individuals from the Poso Pesisir Utara population have larger leaves, up to 21 × 14 cm, whereas distinctly smaller leaves (c.15 × 10 cm) are found in the other populations. Most of the populations show several variable characters such as adaxial leaf lamina colour, which can be reddish-dark green with irregular silvery variegation or light green without any variegation; short (up to 5 mm long) or long (up to 50 mm long) female inflorescence peduncles; 1- or 2-flowered female inflorescences; ovate or lanceolate female flower tepals; ellipsoid or cylindrical ovaries (without wings); and narrow or wider ovary and fruit wings, which can be rounded or cuneate at the base. (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 J. Bot. 79(Begonia special issue, article 405): 1-50. http://doi.org/10.24823/EJB.2022.405)

Specimens

  • Indonesia. Sulawesi. Northern arm of Sulawesi. Western North Sulawesi: Palu-Oti Road, 3 vii 1979, M.M.J van Balgooy 3597 (L); Donggala Regency, Batusuya, 10 viii 2018, W.H. Ardi et al. WI316 (BO, KRB, SING). Central North Sulawesi: Gorontalo: Albert s.n (BO).
    Central Sulawesi Province: Poso Regency, Bancea, 2 viii 2018, W.H. Ardi et al. WI281 (BO, KRB, SING); Poso Regency, Pesisir Utara Poso: 15 ii 2019, W.H. Ardi et al. WI429 (BO, KRB, SING); 15 ii 2019, W.H. Ardi et al. WI434 (BO, KRB, SING). Donggala Regency, Air Terjun Pangansitoli, 5 iii 2020, W.H. Ardi et al. WI690 (BO, KRB, SING). West Sulawesi Province: Pasang Kayu Regency, Gumbasalu Cave, 3 iii 2020, W.H. Ardi et al. WI686 (BO, KRB, SING). (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 J. Bot. 79(Begonia special issue, article 405): 1-50. http://doi.org/10.24823/EJB.2022.405)