Begonia prionota D.C.Thomas & Ardi

Thomas, Daniel C. & Ardi, Wisnu H., 2020, Synopsis of Begonia (Begoniaceae) of southwest Sulawesi and the Selayar Islands, Indonesia, including one new species, Phytotaxa 437 (2), pp. 73-96 : 88-90

10. Begonia prionota D.C.Thomas & Ardi in Thomas et al. (2011: 237) ( Fig. 1 & 6 )

Sect. Petermannia

Type:— INDONESIA. Sulawesi, Sulawesi Selatan, Gunung Rantemario, alt. 2175 m, steep river bank with Impatiens spec. , Begonia aptera , Urticaceae , 27 Apr. 2009, D.C. Thomas & W.H. Ardi 09-97 (holo E[00533468]!, iso BO!, E[00533469]!).

Description:— Perennial, erect, monoecious herb to ca. 80 cm tall. Stem branched; internodes 3‒11 cm long, brownish-reddish, with a sparse to moderately dense indumentum of multicellular, simple hairs ca. 1.5‒3 mm long, and microscopic glandular hairs. Leaves alternate; stipules caducous, 9‒15 × 3‒9 mm, ovate to oblong, midrib abaxially prominent, apex narrowed into bristle 2−4 mm long, abaxially hairy on the midrib, greenish; petioles 3–10 cm long, reddish or brownish, hairy; lamina basifixed, 8–15 × 4–10 cm, ovate to elliptic, asymmetric, leaf margin serrate, biserrate, sometimes shallowly lobed (up to ca. 25% of lamina width), base cordate and lobes not overlapping, apex acuminate, margin dentate to serrate to bidentate or biserrate, teeth bristle-pointed, adaxial surface dark green, hairy; abaxial surface pale green or reddish, hairy; venation palmate-pinnate, primary veins 5–6, actinodromous, secondary veins craspedodromous. Inflorescences: protogynous; female inflorescences 2-flowered, one node below male inflorescence part or separate, peduncles 12‒20 mm long, reddish, sparsely hairy, bracts caducous, 4 × 2 mm, ovate, pale green, translucent, glabrous; male inflorescences paniculate-cymose, composed of 2‒12(‒16) sessile monochasial partial inflorescences, partial inflorescence internodes usually with short, but well-developed basal internodes (0‒) 1‒10 mm long or sometimes all internodes strongly compressed, each with up to 8 flowers, bracts caducous, 2‒6 × 1.5‒3 mm, broadly ovate to suborbicular, pale green or reddish-green, glabrous. Male flowers: pedicels 8–13 mm long, whitish-pinkish; tepals 2, white, 10–17 × 14–16 mm, broadly ovate, base slightly cordate, apex rounded, outer surface glabrous; androecium of 47‒59 stamens, yellow to orange, filaments up to ca. 2.5 mm long, slightly fused at the very base, anthers up to ca. 1 mm long, obovate, dehiscing through unilaterally positioned slits that are> ½ as long as the anthers. Female flowers: pedicels 4−11 mm long, greenish-reddish, sparsely hairy; tepals 5, white tinged with pink, unequal, 4 larger tepals 7–16 × 4–13 mm, elliptic, 1 smaller tepal 7–14 × 3–7 mm, elliptic, tepal margin sometimes irregularly serrate in distal half, outer surface sparsely hairy; ovary 5–8 × 2–4.5 mm (excluding the wings), ellipsoid sparsely hairy to glabrescent, wings 3, subequal, base rounded, apex truncate, widest point up to 4 mm (subapically), wing margin setose and often irregularly denticulate to serrulate, locules 3, placentation axile, placentae bilamellate; style ca. 3−4 mm long, basally fused, 3–branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, branches orange, stigma yellowish-orange. Fruit: dry capsule; peduncles to 25 mm long; pedicels 6−13 mm long, glabrescent; seed-bearing part 14−16 × 6−7 mm (excluding the wings), ellipsoid, wing shape as for ovary, up to 11 mm at the widest point (apically), hairy to glabrescent. Seeds barrel-shaped, ca. 0.3 mm long.

Distribution:— INDONESIA. Sulawesi, South Sulawesi, Latimojong Mountains, Gunung Rantemario and some adjacent limestone karst areas (Eran Batu and the Bambapuang Karst) ( Fig. 1D ).

Habitat:— Primary to severely disturbed upland to montane rain forest on limestone; on steep slopes or lithophytically on rock walls and in rock crevices; full shade to fully sun-exposed; at ca. 1000 to 2200 m elevation.

Notes:— This species is morphologically similar and likely closely related to B. siregarii , which is known from several localities in Tanah Toraja (Bori, close to Danau Limbong, and Kete Kesu) ca. 50 km north of the type locality of B. prionota . Begonia prionota can be differentiated by an indumentum of longer hairs (to ca. 3 mm long), while B. siregarii has a characteristic whitish indumentum of very short hairs (to ca. 0.5 mm long) (see Ardi et al. 2014: Fig. 3C ); a leaf margin that is dentate, serrate, biserrate, and sometimes shallowly lobed (vs margin usually irregularly dentate and denticulate in B. siregarii ); and smaller male flowers (tepals 10–17 × 14–16 mm vs tepals 15–19 × 15–22 mm). Moreover, the ovary wing margins and the female flower tepal margins are frequently serrulate (vs margins entire in B. siregarii ), but this is not always clearly developed.

Provisional IUCN conservation assessment:— Endangered (EN) B1ab(iii),B2ab(iii). This species is only known from a few collections, and most collection localities were in limestone habitats in close proximity to settlements and agricultural land, and showed signs of severe anthropogenic disturbance. Given the poor state and reduction of forest on limestone in South Sulawesi (Cannon et al. 2005, 2007), and the small EOO and AOO, we assess this species as Endangered.

Additional specimens examined:— INDONESIA. Sulawesi, South Sulawesi: Kab. Enrekang, Kec. Baraka, Eran Batu , 1 Sep. 1994, D. Girmansyah 50 ( BO) ; ibid., 1 Sep. 1994, D. Girmansyah 51 ( BO) ; ibid., 1 Sep. 1994, D. Girmansyah 53 ( BO) ; Gunung Rantemario , 27 Apr. 2009, D.C. Thomas & W.H. Ardi 09-98 ( BO, E, L) ; Bambapuang Karst , 3 Nov. 2018, W.H. Ardi 326 ( BO, KRB, SING) ; Eran Batu , 4 Nov. 2018, W.H. Ardi 328 ( BO, KRB, SING) ; ibid., 4 Nov. 2018, W.H. Ardi 332 ( BO, KRB, SING) ; ibid., 4 Nov. 2018, W.H. Ardi 333 ( BO, KRB, SING) .

Figures

FIGURE 1. Distribution maps of Begonia species occurring on the southwestern arm of Sulawesi or the Selayar Islands (georeferenced specimen data from major collections [B, BO, E, K, KRB, L, SING], the Begonia Resource Center [Hughes et al. 2015a], as well as some additional confirmed observations). Grey lines indicate 1° graticules.

FIGURE 3. Begonia enoplocampa. A: Habit. B: Leaf, abaxial, scale bar = 10 cm. C: Rhizome bearing stipules and branched emergences; scale bar = 3 cm. D: Rhizome cross-section, stipule, branched emergences; scale bar = 2 cm. E: Inflorescence; scale bar = 2 cm. F: Male flower, front view, scale bar = 14 mm. G: Female flower, front view; scale bar = 10 mm. H: Female flower, side view; scale bar = 5 mm. I: Fruit, side view; scale bar = 7 mm. J: Ovary cross-section, unilamellate placentation, scale bar = 3 mm.A, J: W.H. Ardi 368. Photos: B-H: D.C. Thomas; A, I, J: W.H. Ardi.

FIGURE 6. Begonia prionota. A: Limestone habitat and growth habit. B: Leaves, abaxial surface, scale bar = 8 cm. C: Stipule; scale bar = 6 mm. D: Male inflorescence; scale bar = 3 cm. E: Male flower, front view; scale bar = 15 mm. F: Infructescence; scale bar = 15 mm. G: Female inflorescence; scale bar = 10 mm. H: Female flower, front view; scale bar = 14 mm. I: Ovary cross-section, bilamellate placentation, scale bar = 3 mm. A-F, I, J: W.H. Ardi 328; G-H: W.H. Ardi 332. Photos: W.H.Ardi.