Begonia kapuashuluensis Randi & Ardi, 2022

Randi, Agusti, Ardi, Wisnu H., Girmansyah, Deden, Sitepu, Bina Swasta & Hughes, Mark, 2022, Three new species, one new record and an updated checklist of Begonia (Begoniaceae) from Kalimantan, Indonesia, Phytotaxa 533 (1), pp. 62-72 : 63

Begonia kapuashuluensis Randi & Ardi , sp. nov., B. sect. Petermannia ( Fig. 1 ).

Type: — INDONESIA, West Kalimantan Province, Kapuas Hulu Regency, Boyan Tanjung District , 0°20'44.84"N, 112°25'4.53"E, 110 m elev., 10 July 2017, A . Randi AR-1022 (holotype BO!) .

Diagnosis:— It is allied to B. darthvaderiana C.W.Lin & C.I Peng ( Lin et al. 2014: 132) in habit and floral characters, but differs in being a smaller plant up to 20 cm (vs. 25–70 cm) height with smaller leaves 9–14 × 4–7 cm (vs. 13–22 × 8–13 cm), deep bluish green (vs. blackish green with a narrow pale margin) leaves, and more stamens (22–31 vs. 7–11).

A small herb, erect, up to 20 cm tall. Stem with 1–3 branches, 4–7 mm in diameter at the base, glabrous, bright red to brownish, fleshy and succulent, internodes 1–3 cm apart. Stipules caducous, asymmetric, translucent, glabrous, elliptic to lanceolate, 10–15 × 3–5 mm, with a stiff main rib and many parallel red veins; margin entire, apex acute with a short-pointed tip; pale green to red to brownish. Leaves 4–7, simple, alternate, oblique, glabrous; petiole 1–4 cm long, red to brownish, glabrous; lamina ovate, 9–14 × 4–7 cm (basal lobes included); strongly asymmetric with a well-developed basal lobe on one side giving a cordate appearance, base unequal, basal lobes 1–3 cm long, margins minutely denticulate, generally with a narrow dark red border adaxially that is clearly visible on young leaves, apex acuminate; adaxially shiny, deep bluish-green, surface flat or slightly bullate, abaxially light red to crimson, glabrous; venation palmate-pinnate, midrib distinguishable, with 3–4 lateral veins each side, other primary veins branching dichotomously; young leaf brownish abaxially. Inflorescence protogynous, terminally or axillary, erect, 6–12 cm long; basal branch with a pair (rarely 2 pairs) of pistillate flowers on short peduncle ca. 1 cm long, often with leaves at the first branch; upper distal to 10 cm long, zig-zag, branching cymosely, peduncle to 5 cm long, cymes branching to 3 orders, crimson to brownish, glabrous; bracts caducous, translucent, glabrous; bract on nodes of pistillate flower elliptic to lanceolate ca. 5 × 1 mm, cream to pinkish, margin entire, apex acute to cuspidate; bracts on higher part of inflorescence similar but smaller. Staminate flower with 2 pink tepals, each tepal ovate to orbicular or obovate, 3–5 × 3–5 mm, glabrous, margin entire, apex acute to rounded; pedicel pink to crimson, 2–5 mm long, glabrous; androecium symmetric with 22–31 yellow stamens, filament 0.6–1.2 mm long, anthers obovate 0.7–1.4 mm long, apex opened by slit. Pistillate flower 10–20 mm across, each flower blooming alternately; pedicel pink to brownish red, 4–8 mm long, ca. 1 mm in diameter, glabrous; ovary 3-locular, asymmetric, 7–11 × 10–15 mm (wings included), yellowish-green in the middle, red to brownish on the wings; tepals 5, glabrous, 2 outer and 3 inner, all pink and elliptic, 6–8 × 4–5 mm, apex acute to obtuse; styles 3, bifid, 2–4 mm long, golden yellow; stigmas narrowly Y-shaped, forming a papillose spiral band. Fruits nodding, 7–15 × 10–18 mm (wings included), pink to crimson, glabrous; wings 3, subequal, nearly parallel but with rounded, apex acute or mucronate, 3–4 mm wide at the widest point.

Distribution: —Endemic to Borneo, widespread in the western part of the Muller Mountains that administratively belong to Kapuas Hulu Regency of West Kalimantan Province, Indonesia.

Habitat: —Humid areas near rivers or narrow valleys under a dense canopy of mixed dipterocarp forest at 100– 300 m elev.

Etymology: —The epithet refers to the name of regency where this species was found, Kapuas Hulu.

Provisional Conservation Status: —Near threatened (NT) ( IUCN, 2019). This species is observed in seven localities and locally abundant in the western part of Muller Mountains. Although based on EOO = 184.6 km ² and AOO = 28 km ² this species potentially qualifies for the endangered category, but we have observed that this species is growing in relatively undisturbed forest and in several protected forest areas. However, the populations could be threatened due to extraction by plant hunters to be sold as an ornamental, as this beautiful species is well known among Begonia enthusiasts. It has the popular trade name Begonia “temuyuk” and is for sale on commercial and social media sites for prices ranging from 50 US dollars to 160 Euros. Traditional cultivation activity is also observed near the populations. In the future, these threats could drive the taxon to VU or even EN in a short time.

Notes: —Unlike most other erect species of Begonia sect. Petermannia in Borneo, B. kapuashuluensis has a very short stem not exceeding 20 cm tall. Apart from its small size, B. kapuashuluensis is distinctive in having deep bluish green leaves which are light red to crimson beneath, often with a small cauline leaf at the first branch of the inflorescence.

Figures

FIGURE 1. Begonia kapuashuluensis Randi & Ardi. A. Plant habit; B. Leaves abaxial surface; C. Inflorescence; D. Stipule; E. Staminate flowers; F. Bract; G. Staminate flower (side view); H, I. Top and side views of pistillate flower; J. Mature fruits; K. Cross section of fruit. Scale bars: B: 5 cm, C: 3 cm, D–K: 5 mm. Photo A, C–J: A. Randi AR-1022; B & K: Wisnu H. Ardi.