Begonia hekensis D.C.Thomas in Edinburgh J. Bot. 66(1): 110. 2009

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Content

Begonia Section

  • Petermannia

Diagnosis

  • Begoniae hispidissimae Zipp. ex Koord. similis a qua pedunculis inflorescentiarum feminearum longioribus, pedicellis capsularum valde deflexis differt. - Type: Indonesia, Sulawesi, Sulawesi Tengah, Luwuk District, Bunta Subdistrict, Sumber Agung, Gunung Hek, riverbank near small waterfall, 01°01'72.2S, 122°11'54.7E, 1009 m, 12 iv 2008, D.C. Thomas & W.H. Ardi 08-43 (holo E; iso BO, CEB). (Thomas, D.C., Ardi, W.H. & Hughes, M. 2009: Two new species of Begonia (Begoniaceae) from Central Sulawesi, Indonesia. – Edinburgh Journal of Botany 66(1): 103-114)

Description

  • Perennial, monoecious, erect herb, to c.100 cm tall, hairy with up to c.1.2 mm long, multicellular, multiseriate, simple trichomes and microscopic, glandular trichomes on all vegetative parts.

    Stems branched; internodes 2.2-8.3 cm long, densely hairy.

    Leaves alternate; stipules 8-28 × 2-10 mm, narrowly ovate, cymbiform with abaxially prominent midrib forming a thin, short appendage at the apex, persistent, abaxially densely hairy; petioles 0.7-11.2 cm long, densely hairy; lamina basifixed, 2.5-15.2 × 1.1-8.2 cm, very asymmetric, ovate or elliptic, base cordate with non- or only very slightly overlapping lobes, apex acuminate, margin dentate to serrate, teeth bristle-pointed, abaxial surface hairy, adaxial surface sparsely hairy, adaxial surface mid green and abaxial surface pale green, venation palmate-pinnate.

    Inflorescences protogynous; female inflorescences basal to male inflorescences or solitary, 2-flowered, subtending leaves foliose, peduncles 2.6-3 cm long (in fruit), bracts (subtending the pedicels of the female flowers) c.16 × 6 mm, narrowly elliptic, abaxially hairy; male inflorescences distal to one female inflorescence or solitary, subtending leaves frondose-bracteose (lamina strongly reduced in size), peduncle 9-12 mm long, bracts (subtending the lateral branches) 4-12 × 1-6 mm, oblong, the basal ones abaxially hairy, the distal ones glabrous, a once-branched dichasium or with one dichotomous branching at the base, and each of the two resulting branches branching once dichasially, sometimes the lateral branches of the dichasia branching once monochasially.

    Male flowers: pedicels 4-23 mm, hairy; tepals 2, white, 11-18 × 10-18 mm, broadly ovate to subcircular, base cordate or tepal margin convex at base, apex rounded, abaxially sparsely hairy; androecium of c.24-38 stamens, yellow, filaments c.0.4-2 mm long, slightly fused at the very base, unequal, longer in the middle of the androecium, anthers c.1-2 mm long, obovate or oblong, dehiscing through unilateral positioned slits < 1/2 as long as the anther, connective not projecting.

    Female flowers: unknown.

    Fruits: capsules ellipsoid, 14-17 × 5-8 mm (without wings), on apically strongly deflexed, 18-24 mm long, hairy pedicels, dehiscent, splitting along the wing attachment, drying brown, hairy, locules 3, placentation axile, placentae bilamellate, wings 3, sublunate, base rounded, widest in the middle to subapical part, subequal, one slightly larger than the other two, 7-8 mm wide in the widest part, the smaller two 6-7 mm in the widest part, hairy. Seeds ellipsoidal, c.0.3-0.4 mm long, collar cells c.1/3-1/2 of the length of the seed. (Thomas, D.C., Ardi, W.H. & Hughes, M. 2009: Two new species of Begonia (Begoniaceae) from Central Sulawesi, Indonesia. – Edinburgh Journal of Botany 66(1): 103-114)

Habitat

  • This is an upland species which grows in the herb layer of primary rainforests, often along the sides of small streams, at c.850-1200 m.

Conservation

  • Proposed IUCN conservation category: VU D2. This species is known only from Gunung Hek and has a very restricted range in an area which has no legal protection as a national park or nature reserve. Although the forest is in good condition in this area at around 1000 m, there are clear signs of anthropogenic disturbance, especially selective timber harvesting and rattan collection, at slightly lower altitudes. Therefore, the populations are "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. & Hughes, M. 2009: Two new species of Begonia (Begoniaceae) from Central Sulawesi, Indonesia. – Edinburgh Journal of Botany 66(1): 103-114)

Distribution

Asia-Tropical: Sulawesi (Sulawesi endemic)
Endemic to Indonesia, Sulawesi, Central Sulawesi.

See specimen tab for map of point distribution data of georeferenced specimens.

Etymology

  • The epithet "hekensis" is composed of "Hek", a reference to Gunung Hek where the type material was collected, and "-ensis" (Latin - originating from).

Notes

  • Begonia hekensis is morphologically similar to Begonia hispidissima and Begonia masarangensis Irmsch. These three species exhibit a character combination which differentiates them from most other Sulawesian Begonia section Petermannia species: densely hairy stems and petioles, few-flowered male inflorescences, male flowers with abaxially hairy tepals, and short, hairy ovaries and capsules. However, Begonia hekensis can be easily differentiated from Begonia masarangensis by its ovate to elliptic leaves with a dentate to serrate margin and the compressed, purely, or at least partially, dichasially branching male inflorescences (versus oblong to narrowly elliptic leaves with double serrate margin and purely monochasially branching male inflorescences). Begonia hekensis differs from B. hispidissima by the apically strongly deflexed pedicels of the fruits and the peduncles of the female inflorescences which may be up to 3 cm long (versus not or only slightly deflexed pedicels and peduncles up to c.1.5 cm long in B. hispidissima). (Thomas, D.C., Ardi, W.H. & Hughes, M. 2009: Two new species of Begonia (Begoniaceae) from Central Sulawesi, Indonesia. – Edinburgh Journal of Botany 66(1): 103-114)

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

  • SULAWESI. Tengah: Luwuk District, Bunta Subdistrict, Sumber Agung, Gunung Hek, Sungai Hek, between Cabang Tiga and Agathis Camp, 01°019100S, 122°109300E, 980 m, 1 iii 2004, Hendrian, M. Newman, S. Scott, M. Nazre Saleh & D. Supriadi 1015 (E); Sumber Agung, Gunung Hek, side of steep track, 01°01958.20S, 122°10990.90E, 870 m, 10 iv 2008, D.C. Thomas & W.H. Ardi 08-30 (BO, CEB, E); Sumber Agung, Gunung Hek, small isle in Sungai Hek, 01°01981.20S, 122°11935.00E, 1080 m, 11 iv 2008, D.C. Thomas & W.H. Ardi 08-33 (BO, CEB, E); Sumber Agung, Gunung Hek, side of small tributary of Sungai Hek, 01°01976.00S, 122°11942.40E, 993 m, 12 iv 2008, D.C. Thomas & W.H. Ardi 08-41 (BO, CEB, E). (Thomas, D.C., Ardi, W.H. & Hughes, M. 2009: Two new species of Begonia (Begoniaceae) from Central Sulawesi, Indonesia. – Edinburgh Journal of Botany 66(1): 103-114)