Begonia tomaniensis Rimi, 2015

Repin, Rimi, Sang, Julia, Kiew, Ruth & Mujih, Handry, 2015, Eleven new species of Begonia (Begoniaceae) from the Crocker Range, Sabah, Malaysia, Phytotaxa 208 (1), pp. 1-20 : 17-19

11. Begonia tomaniensis Rimi , spec. nov. ( Figure 12 )

Section uncertain

In leaf shape it is similar to Begonia gibbsiae Irmscher ex Sands (2001: 154) but is different in its leaves with maroon hairs (not glabrous as in B. gibbsiae ), short petiole, 1.2–1.5 mm long (not 8–30 mm), larger lamina 7–10 × 3.5–8.5 cm (not 3–7.5 × 1.7–7.2 cm), its shorter inflorescence 1.2–2 cm long (not 13(–20) cm long), its male flowers with 2 tepals (not 4 tepals) and its locules each with a single placenta (not bilamellate). From all other Bornean begonias it differs in its leaf venation where the midrib bifurcates in the lower half of the leaf to produce two equal veins.

Type:— MALAYSIA. Borneo. Sabah. Tenom District: Crocker Range, Ulu Tomani, Simambo river, 12 July 2011, Rimi et al. SNP 21903 (holotype SNP!).

Erect herb to 30 cm tall. Stem rarely branched, greenish brown, ca. 0.4 mm thick, woody, hispid, hairs ca. 0.5 mm long; internodes 2.5–4.5 cm long. Stipules brown, hispid, broadly lanceolate, ca. 15 × 5 mm, margin entire, apex acuminate, persistent. Leaves alternate, not oblique, distant, held horizontally; petiole brownish, hispid, 1.2–1.5 cm long, slightly grooved above; lamina plain green with maroon hairs above, hairs 3–5 mm long, maroon and hairy below, papery when fresh, matt, obovate to rotund, slightly asymmetrical, 7–10 × 3.5–8.4 cm, base rounded, basal lobes scarcely developed, margin minutely dentate, apex rounded; venation palmate, midrib ca. 2 cm long, bifurcates in the lower half of the leaf, veins 3 at the base of midrib, dichotomise twice before reaching the margin, prominent on both surfaces but more prominent beneath. Inflorescences protogynous, axillary in upper leaf axils, erect, cymose, rachis 12–20 mm long, peduncle ca. 7 mm long. Bracts whitish, oval, 4–9 × 2 mm (on male flower), 3–7 × 2–3 mm (on female flower), margin entire, glabrous, caducous; bracteoles whitish, lanceolate, ca. 3 × 2 mm, margin entire, glabrous, persistent. Female flower: pedicel 8–10 mm long, white, sparsely hairy; ovary pale green, ovoid, 0.8–1 × 1–1.4 cm, sparsely hairy, wings 3, equal, locules 3, placenta 1 per locule with many ovules on both surfaces; tepals 5, white tinged pink, sparsely hairy outside, margin entire, apex acute, outermost tepals 10–11 × 5–7 mm, innermost tepals 10 × 2 mm; styles 3, yellow, 4–5 mm long, divided to base, Y-shaped with an almost flat top; stigma yellow, papillose forming a continuous twisted band. Male flower: pedicel white or pale pink, 1.4–2 mm long, glabrous; tepals 2, greenish white, glabrous, broadly oval, ca. 4 × 4 mm, margin entire, apex acute; stamens ca. 20, cluster loosely conical, sessile; filaments lemon yellow, 1.4–2 mm long; anthers lemon yellow, oblong or obovate, ca. 1 × 0.3 mm, apex emarginate. Capsule: pedicel stiff, ca. 0.5 cm long; fruit ca. 1 × 1.2 cm, hispid, hairs white, wings equal, pointed proximally, pointed to trunctate distally, ca. 0.5 cm wide, thinly fibrous, dehiscing between locule and wing. Seed: barrel-shaped, columnar cells more than half the length of seed.

Distribution: — MALAYSIA. Borneo. Sabah. Tenom District. Endemic in Ulu Tomani.

Habitat: —Secondary forest, under shade along riverside at 900 m elevation.

Etymology: —It is named for the locality from where it was first collected.

Additional specimens examined: — MALAYSIA. Borneo. Sabah. Tenom District: Crocker Range– Ulu Tomani, Simambo River, Geofarry et al. SNP 21902 (SNP).

Notes: —This species is unique among Bornean begonias for its venation where the midrib bifurcates into two equal veins about 2 cm above the petiole, these two veins then further dichotomise until they reach the margin.

Its undivided placenta would place this species in sect. Reichenheimia , which would make it the only species in Sabah to belong to this section. However, Begonia chongii Sands (2001: 150) also has an undivided placenta but is clearly allied with the B. cauliflora Sands (1990: 68) group of Bornean begonias that belong to sect. Petermannia . In addition, the illustration of this latter species suggests that the placentas are not fully developed. Begonia tomaniensis is a small plant with rounded leaves similar to those found in sect. Reichenheimia but also to Sabah species in sect. Petermannia , such as B. gibbsiae Irmsch. ex Sands (2001:154) . We therefore refrain from placing Begonia tomaniensis in sect. Reichenheimia . Molecular analysis is called for to solve the placement of this species.

Figures

FIGURE 12. Begonia tomaniensis. A. Habit. B. Unopened male inflorescence; C. Male flower; D. Fruit. All photos SNP 21903 by Rimi Repin.