Begonia rubrobracteolata S.Julia & C.Y.Ling, 2016

Sang, Julia, Kiew, Ruth & Yiing, Ling Chea, 2016, Six new species of Begonia (Begoniaceae) from Central Sarawak, Borneo, Phytotaxa 277 (2), pp. 171-181 : 176-177

4. Begonia rubrobracteolata S.Julia & C.Y.Ling , spec.nov. ( Figure 5 )

Section Petermannia

Diagnosis: —Close to Begonia linauensis S. Julia (2015: 144) in its habit, leaf shape and the inflorescence type but it differs in having pilose stems and stipules and erect, stiff hairs on its leaves (vs. a pubescent stem and glabrous stipules and leaves), its wider stipules 5–6.5 mm wide (vs. ca. 3 mm wide), leaf base cordate with basal lobe 2–5 mm wide (vs. base rounded with inconspicuous basal lobe), the leaf margin is minutely serrate and covered with hispid hairs (vs. minutely dentate and glabrous), its rachis 8.5–15 cm long (vs. 3.5–5 cm long), the bracts and bracteoles with ciliate margins (vs. entire margins) and bracteole pairs 6–10 (vs. 3–5 pairs), shorter pedicel of male flower 7–9 mm long (vs. 12–14 mm long) and female flowers sessile (vs. female flowers with pedicels 0.4–1 mm long), fewer stamens 9–12 (vs. 28–35) and its female flower with shorter ovary 4–5 mm long (vs. 7–12 mm), shorter outer and inner tepals (6–8 mm long and 4–6 mm long respectively vs. 10–12 mm long and 10–11 mm long in B. linauensis ).

TYPE: — Borneo , Sarawak, Kapit District , Bukit Batu Mado, 8 August 2015, Jacqualine et al. SFC 5868 (holotype SAR!; isotype KEP!) .

Low herb to 25 cm tall, sometime decumbent. Stems, stipules, petioles and peduncle covered with sparse short reddish pilose hairs. Leaves with sparse erect stiff dark red hairs between the veins on upper leaf surface, along the veins on lower leaf surface and along the leaf margin. Stems light to dark brown, 3.5–4 mm thick, internodes 1.8–2.8 cm long, few-branched on lower stem, succulent, thicker at nodes. Stipules pale red-brown to pinkish, ovate, 10–13 × 5–6.5 mm, margin ciliate, apex acute, persistent. Leaves alternate, distant, slightly oblique, held horizontally; petioles pale red, 1.3–3 cm long, slightly grooved above; lamina dark olive green above, maroon beneath, in life succulent, shiny, asymmetric, sub-orbicular, (3.5–)5–6 × 4.5–6 cm, narrow side 2–3.7 cm wide, base cordate, not overlapping, basal lobes 2–5 mm long, margin minutely serrate, apex rounded to broadly acute; venation palmate-pinnate, veins dark green to green-brown above, pale red beneath, 3–5 veins on either side of the midrib, 1–2 veins in basal lobe, distinctly impressed above, raised beneath. Inflorescences protogynous, axillary on upper leaf, paniculate, rachis 8.5– 15 cm long. Bracts reddish, ovate, 6–8 × 5–6 mm, margin ciliate, persistent; bracteoles 6–10 pairs, lower bracteoles similar to bracts, reddish, 5–7 × 4–5 mm, upper bracteoles dark red, oval, 4–6 × 5 mm, margin ciliate, apex broadly acute, persistent. Male flowers: pedicel red, 7–9 mm long, glabrous; tepals 4, glabrous; outer 2 tepals reddish outside, reddish-white inside, broadly elliptic, 6–10 × 6 mm, margin entire, apex broadly acute; inner 2 tepals reddish at the base, otherwise white, lanceolate, 5–8 × 2–4 mm, margin entire, apex broadly acute; stamens 9–12, cluster conical, subsessile; filaments pale yellow, ca. 0.8 mm long; anthers pale yellow, obovate, ca. 1 × 0.4 mm, apex emarginate. Female flowers: sessile; ovary pinkish, broadly elliptic, 4–5 × 8–10 mm, glabrous, wings 3, equal, locules 3, placenta 2 per locule; tepals 5, rarely 6, glabrous, margin entire, outer 3–4 tepals pinkish outside, pinkish-white inside, broadly elliptic, 6–8 × 5–6 mm, apex broadly acute, inner 2 tepals white, lanceolate, 4–6 × 2–3 mm; styles 3, pale yellow, ca. 1 mm long, divided to base, anchor-shaped; stigma pale yellow, papillose forming a continuous twisted band. Capsules not seen.

Etymology: —Latin, rubra = red; referring to its red bracteoles

Distribution: —Endemic in Sarawak. Known only from the type locality.

Habitat: —On sandstone boulders and shaded areas with thick leaf litter.

Proposed conservation status: —Critically Endangered as the species is known only from a locality that lies outside the network of Totally Protected Areas and is subjected to forest conversion and habitat disturbance.

Figures

FIGURE 5. Begonia rubrobracteolata.A, Habit; B, Close-up of leaf surface; C, Stipule; D, Inflorescence showing the bract and bracteoles; E, Bracts and bracteoles; F–G, Male flower; H–I, Female flower; J, Cross-section of ovary. All photos from SFC 5868 by C.Y.Ling.