Begonia labengkiensis Ardi & D.C.Thomas, Edinburgh Journal of Botany 80: article 1980, 11. 2023

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Content

Begonia Section

  • Petermannia

Diagnosis

  • Distinguished by the basal stem that is appressed to the substrate, the long-pedunculate female inflorescences, and the paniculate-cymose male inflorescences. Morphologically similar to Begonia matarombeoensis, but B. labengkiensis can be differentiated by its apiculate stipules (apicule 1 mm long vs seta at stipule apex to 6 mm long); leaves adaxially bullate, each bulla tipped with a white pilose hairs (vs not bullate and glabrous); bract of female inflorescence ovate, cymbiform (vs elliptic); tepals of male and female flowers orange (vs white or white tinged with pink); female flower pedicel 5–9 mm long, recurved (vs 9–11 mm, not recurved); ovary shape (without wings) obovoid to narrowly obovoid (vs ellipsoid) (Table 2). (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)

Description

  • Perennial, monoecious herb, basal stem appressed to the substrate and rooting at the nodes, distally often ascending to erect, many branched. Stem succulent, up to 1.2 cm in diameter, greenish-brownish, with microscopic glandular hairs and a few villose hairs to glabrescent, internodes 1–4 cm long. Leaves alternate; stipules persistent, 8–12 × 6–13 mm, broadly ovate, asymmetrical, with an abaxially slightly prominent midrib from the middle part to the apex, apex apiculate, apicule up to 1 mm long, margin crenate, and crenulate between the larger teeth, ciliate, reddish, glabrous; petioles 11–22 cm long, terrete, pale orange, sparsely pilose hairy; lamina 12–20 × 8.5–14 cm, asymmetrical, ovate to broadly ovate, base cordate and lobes sometimes overlapping, apex acuminate, margin crenate-crenulate, ciliate, adaxial surface reddish green, slightly bullate, bullae tipped by white pilose hairs, abaxial surface red, pale orange on the veins, hairy on the veins, primary veins 7 or 8, actinodromous, secondary veins craspedodromous. Inflorescences: protogynous; female inflorescences 1- or 2-flowered, basal to male inflorescences, peduncles 2–3 cm long, becoming shorter in the distal part, red, glabrous, bracts persistent, 4–5 × 3–4 mm, ovate, asymmetrical, cymbiform, reddish, translucent at the margin, midrib slightly prominent; male inflorescences paniculate-cymose, composed up to 12 subumbellate partial inflorescences, each with up to 10 flowers, peduncles of partial inflorescence up to 3.5 cm long, reddish, glabrous; bracts persistent, 2–6 × 2–4 mm, ovate, asymmetrical, apiculate, apicule up to 0.5 mm long at the apex. Male flowers: pedicels 4–11 mm long, orange, glabrous; tepals 2, orange-yellowish, 5–12 × 7–12 mm, broadly ovate, base slightly cordate, margin entire, apex rounded; androecium of c.22 stamens, yellow, filaments up to c.1 mm long, anthers up to 0.75 mm long, obovate, dehiscing through unilaterally positioned slits that are c.1/2 as long as the anthers. Female flowers: pedicels 5–9 mm long, reddish, slightly recurved, glabrous; tepals 5, orange-yellowish, subequal or unequal, four larger 11–13.5 × 9–11 mm, ovate, one smaller c.11 × 5 mm, elliptic, margin entire, apex rounded; ovary (without wings) 7.5–8.5 × 4–6 mm, obovoid to narrowly obovoid, reddish, glabrous, wings 3, subequal, rounded to cuneate at base and truncate to subtruncate at apex, up to 2.5–4.5 mm at the widest point (apical to subapical), style up to 4.5 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruit: peduncle up to 4 cm long; pedicels 10–15 mm long, strongly recurved; seed-bearing part c.9–16 × 4–7 mm (excluding the wings), obovoid to narrowly obovoid, dehiscent, splitting along the wing attachment, wing shape as for ovary, up to 8 mm long at the widest point (apically or subapically). Seeds barrel-shaped, c.0.3 mm long. (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)

Habitat

  • Crevices on vertical limestone hill, coastal karstic forest, shaded, at 1 m elevation (see Figure 2B). (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)

Conservation

  • Proposed IUCN conservation assessment. Critically Endangered CR B1ab(i,ii,iii)+2ab(i,ii,iii). This species is known only from the type location, Labengki Besar Island, which has no legal protection status. The species is restricted to limestone cliffs. During fieldwork, fewer than 10 mature individuals were observed. There were no signs of direct anthropogenic threats such as limestone mining observed during fieldwork, but some forest cover loss of about 1 ha in 2016, predominantly due to fire, is indicated by remote-sensing data within a 2-km buffer from the type locality (Global Forest Watch, 2023). Given the very small AOO (4 km2), a single known location, and the observed forest cover loss in close proximity to the type locality, we assess this species as Critically Endangered (IUCN Standards and Petitions Subcommittee, 2022). (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)

Distribution (General)

  • Indonesia, endemic to Sulawesi, southeastern Sulawesi, Labengki Besar Island (see Figure 3). (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)A
A. Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980

Etymology

  • The species epithet refers to Labengki Island, southeastern Sulawesi, where the type material was collected. (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)B
B. Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980

Notes

  • Begonia labengkiensis has orange tepals, which is very rare in Sulawesi species from Begonia sect. Petermannia. There are only two species in Sulawesi that share this character: Begonia ignita C.W.Lin & C.I Peng and B. tjiasmantoi Ardi & D.C.Thomas (Lin et al., 2017; Ardi & Thomas, 2019). Begonia labengkiensis can be easily distinguished from these two species by the character combination shown in Table 2. (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)

Specimens

  • Indonesia. Sulawesi: Southeastern Sulawesi: Cultivated specimen collected from the wild, Labengki Besar, North Cliff, Tapu Batusahan, 27 vi 2022, W.H. Ardi WI772 (FIPIA); Labengki Besar, north cliff, Tapu Batusahan, 29 vi 2022, W.H. Ardi WI774 (FIPIA, UI). (Ardi, W.H. & Thomas, D.C. 2023: Three new species of Begonia from the outer islands of Southeast Sulawesi. – Edinburgh J. Bot. 80(article 1980): 4. http://doi.org/10.24823/EJB.2023.1980)