Begonia didyma D.C.Thomas & Ardi in Edinburgh J. Bot. 66(2): 230. 2009

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Begonia Section

  • Petermannia

Diagnosis

  • Begoniae gemellae Warb. ex L.B.Sm. & Wassh. similis a qua in caule, foliis et in tepalorum faciebus abaxialibus pilos multicellulares habenti, inflorescentia mascula semper biflora (non biflora ad quinqueflora), pedunculis inflorescentiarum feminearum brevioribus et pedicellis florum feminearum brevioribus differt. - Type: Cultivated at Bali Botanic Garden from vegetative material collected in the wild (Indonesia, Sulawesi, Sulawesi Selatan, Luwu District, Latimojong Mountains, Ranteballa village, 03°21'20S, 120°07'36E, 1225 m), 16 v 2008, D.C. Thomas & W.H. Ardi 08-77 (holo E; iso BO). (Thomas, D.C., Ardi, W.H., Hartutiningsih & Hughes, M., Two new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia in Edinburgh Journal of Botany 66(2). 2009)

Description

  • Perennial, monoecious herb with prostrate to erect stems, to c.35 cm tall, with a moderate to dense indumentum of multicellular, simple trichomes up to c.2 mm long and a sparse indumentum of microscopic, glandular trichomes on all aboveground vegetative parts.

    Stems much-branched, rooting at the lower nodes; internodes c.2-6 cm long.

    Leaves alternate; stipules persistent, 10-15 × 2-5 mm, elliptic, with an abaxially prominent midrib that projects up to c.4 mm at the apex, abaxially densely hairy along the midvein; petioles 2.5-5.6 cm long; lamina basifixed, 4.2-6.7 × 2.6-4.7 cm, very asymmetric, elliptic, base cordate, lobes not overlapping, apex acuminate, margin double serrate to double dentate, the teeth bristle-pointed, adaxial surface mid green and abaxial surface pale green, the margin reddish, venation palmate-pinnate.

    Inflorescences: female flowers solitary, basal to or not associated with the male inflorescences, branches bearing the female flowers c.1-2 mm long, subtending leaf foliose, 2 bracts present at the base of the pedicels of the female flowers, c.2-3 × 2-3 mm, broadly ovate; male inflorescences distal to or not associated with the female flowers, composed of 1-2 two-flowered partial inflorescences, each a once-branched monochasium, subtending leaves foliose, peduncles 2-7 mm long, bracts (subtending the pedicels) c.2-3 × 2-3 mm, elliptic to subcircular.

    Male flowers: pedicels 17-27 mm long, sparsely hairy; tepals 2, white or white with a tinge of pink, 12-17 × 10-14 mm, broadly ovate, base slightly cordate or with convex margins, apex rounded, abaxially sparsely hairy; androecium of c.35-43 stamens, yellow, filaments c.0.6-1.4 mm long, slightly fused at the very base, anthers c.0.9-1.2 mm long, obovate, dehiscing through unilaterally positioned slits c.1/2 as long as the anther, connective not projecting.

    Female flowers: pedicels 2-3 mm long, hairy; tepals 5, white, unequal, the two outer ones 12-13 × 10-12 mm, broadly obovate or elliptic, the two larger inner ones 13-14 × 8-9 mm, obovate, the smallest inner one 8-13 × 3-6 mm, obovate, abaxially sparsely hairy; ovary 10-13 × 11-14 mm, ellipsoid, locules 3, placentation axile, placentae bilamellate, wings 3, narrowly triangular, rounded at base, widest at the truncate apex, hairy, style basally fused for c.1.5-2 mm, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, yellow.

    Fruits on thin, c.3-4 mm long, sparsely hairy pedicels; capsules ellipsoid, c.9-10 × 5-6 mm (excluding the wings), dehiscent, splitting along the wing attachment, drying pale brown, sparsely hairy, wing shape as for ovary, 4-7 mm wide at the widest point (at the apex), hairy. Seeds unknown. (Thomas, D.C., Ardi, W.H., Hartutiningsih & Hughes, M., Two new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia in Edinburgh Journal of Botany 66(2). 2009)

Habitat

  • Upland primary rain forest, on rocky ground, between c.1000 and 1250 m.

Conservation

  • Proposed IUCN conservation category: VU D2. This species is only known from two collections on the eastern border of the Latimojong Forest Reserve. Despite the area?s legal protection as a forest reserve, there are clear signs of anthropogenic disturbance (coffee plantations) close to the locality of this species. All available Begonia specimens from A, B, BM, BO, CEB, E, K, L and SING have been consulted, and hence it must be assumed, at least until more intensive collecting on Sulawesi may reveal otherwise, that this species has a very restricted range. Therefore, it is "prone to the effects of human activities or stochastic events within a very short time period in an uncertain future" (IUCN, 2001). (Thomas, D.C., Ardi, W.H., Hartutiningsih & Hughes, M., Two new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia in Edinburgh Journal of Botany 66(2). 2009)

Distribution

Endemic to Indonesia, Sulawesi, South Sulawesi.
See 'Specimens' tab for map of point distribution data of georeferenced specimens.

Etymology

  • The epithet "didyma" (Greek didymos - twin) refers to the two-flowered male inflorescences of this species.

Notes

  • Begonia didyma is morphologically similar to Begonia gemella Warb. ex L.B.Sm. & Wassh. Both species exhibit relatively thin stems rooting at the nodes, few-flowered monochasial male inflorescences and solitary female flowers. However, Begonia didyma can easily be distinguished from Begonia gemella by its moderate to dense indumentum of up to c.2 mm long, multicellular trichomes on all above-ground vegetative parts and on the tepals and the ovary of the female flowers (versus only sparsely and microscopically glandular hairy in B. gemella). The male inflorescences of Begonia didyma are strictly 2-flowered monochasial without any rudimentary, unopened flowers (Fig. 1H), while the male inflorescences of Begonia gemella are few-flowered monochasial (2-5-flowered). Warburg (see Koorders, 1904) probably chose the epithet "gemella" (Latin - twin) as reference to the male inflorescences of Begonia gemella, which predominantly show two fully developed flowers, but an examination of recently collected material of this species (K. Armstrong 364 at E), as well as the illustration in Koorders- Schumacher (1922: pl. 94) and a sketch by Irmscher on a herbarium sheet of type material of Begonia gemella (S.H. Koorders 16243b at B), show that the male inflorescences of this species comprise two to five flowers. Moreover, Begonia didyma exhibits very compressed branches bearing the female flowers (up to 2 mm long) and very short pedicels of the female flowers and fruits (up to 4 mm long), while in Begonia gemella these structures, though still short, are distinctly longer than in B. didyma (the branches bearing the female flowers are 5-25 mm long and the pedicels of the female flowers and fruits are 7-18 mm long). (Thomas, D.C., Ardi, W.H., Hartutiningsih & Hughes, M., Two new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia in Edinburgh Journal of Botany 66(2). 2009)

Specimens

  • SULAWESI. South Sulawesi: Luwu District, Latimojong Mountain Range, Desa Lambanan Dusun Tibusan, 2 xi 1994, J.P. Mogea, M. Amir & H. Alrasyid 6596 (BO). (Thomas, D.C., Ardi, W.H., Hartutiningsih & Hughes, M., Two new species of Begonia (Begoniaceae) from South Sulawesi, Indonesia in Edinburgh Journal of Botany 66(2). 2009)