Begonia batusangiensis Ardi & D.C.Thomas, 2023

Ardi, Wisnu H. & Thomas, Daniel, 2023, THREE NEW SPECIES OF BEGONIA FROM THE OUTER ISLANDS OF SOUTHEASTERN SULAWESI, Edinburgh Journal of Botany 80 (1980), pp. 1-17 : 4-8

1. Begonia batusangiensis Ardi & D.C.Thomas , sp. nov. § Petermannia

Begonia batusangiensis has female flowers with 2 tepals, recurved pedicels, and a fusiform ovary with very narrow (up to 2 mm) wings, which distinguish it from all other species of Begonia sect. Petermannia with 2-tepaled female flowers ( Table 1). – Type: Indonesia, Sulawesi, Southeast Sulawesi, Gunung Batusangia, 25 vi 2022, W. H. Ardi WI767 (holotype FIPIA; isotypes CEB, SING). Figures 1 , 2A .

Perennial, monoecious herb with basal stem appressed to the substrate, rooting at the nodes, and distally ascending. Stem erect, succulent, semi-woody, up to 1 cm in diameter, brown, glabrous, internodes (0.5–) 4.5–8 cm long, shorter in the most distal parts, younger stem reddish on upper part. Leaves alternate; stipules caducous, 8–10 × 5 mm, elliptic,

with an abaxially weakly prominent midrib from the middle part to the apex, apex apiculate, apicule up to 1 mm long, margin entire and revolute in mature stipules, reddish-greenish, glabrous; petioles 1.5–8 cm long, terrete, red or reddish-brownish, glabrous; lamina 4–7.5 × 2.5–4.5 cm, asymmetrical, succulent, ovate to elliptic, base cordate and lobes sometimes slightly overlapping, apex acuminate, margin serrate, adaxial surface green to reddish green, glabrous, abaxial surface reddish, with sparse hairs on the veins; primary veins 6

or 7, actinodromous, secondary veins craspedodromous. Inflorescences: protogynous; female inflorescences 1- or 2-flowered, basal to male inflorescences, peduncles 1–10 mm long, pale green-reddish, glabrous, bracts caducous; male inflorescences cymose, a simple monochasium with up to 3 flowers or a dichasium with 5–9 flowers, peduncles 10–12 mm long, reddish, glabrous; bracts caducous, up to c.3 × 2 mm, ovate, pale green or creamy at base and reddish at the apex, midrib slightly prominent, apex apiculate, apicule up to

0.5 mm long. Male flowers: pedicels 1–2.2 cm long, pinkish, glabrous; tepals 2, white or pink, 10–19 × 13–21 mm, broadly ovate, base slightly cordate, margin entire, apex rounded; androecium of 35–37 stamens, yellow, filaments up to c. 1.5 mm long, fused at the base for c. 1 mm, anthers up to 1 mm long, obovate, dehiscing through unilaterally positioned slits that are c.1/2 as long as the anthers. Female flowers: pedicels 7–9 mm long, reddish, glabrous, recurved; tepals 2, white or white tinged with pink, 14–16 × 15–17 mm, broadly ovate, margin entire, apex rounded; ovary (without wings) c.10 × 4 mm, fusiform, pale green to reddish green, wings 3, very narrow, up to 2 mm at the widest point (middle part), cuneate at the base and apex, style up to 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 10 mm long; pedicels 15–20 mm long, strongly recurved; seed-bearing part c.13–15 × 8–10 mm (excluding the wings), ellipsoid, dehiscent, splitting along the wing attachment, wings equal, base rounded to cuneate, apex cuneate, up to 2 mm at the widest point (middle part). Seeds barrel-shaped, c. 0.3 mm long.

Distribution. Indonesia; endemic to Sulawesi, southeastern Sulawesi, Kabaena Island, Gunung Batusangia ( Figure 3 ).

Habitat and ecology. Crevices of a vertical limestone hill, open, at 950–1250 m elevation (see Figure 2A ).

Etymology. The species epithet refers to the Batusangia peak on Kabaena Island, southeastern Sulawesi, where the type material was collected.

Proposed IUCN conservation category. CR B1 ab(i,ii,iii)+2ab(i,ii,iii). Begonia batusangiensis is known only from the type location on Gunung Batusangia , Kabaena Island , which is not in a legally protected area. The species is found restricted to limestone cliffs in the upper part of the mountain. Most of the vegetation of the lower part of the mountain has been converted to clove plantations, and there are substantial nickel-mining operations in the vicinity. Owing to its restricted distribution (a single location) and associated small extent of occurrence ( EOO) and area of occupancy ( AOO), in combination with observed anthropogenic disturbances that are negatively affecting the margins of the species’ habitats and are likely to result in further habitat loss in the future, we assess this species as Critically Endangered ( IUCN Standards and Petitions Subcommittee, 2022) .

Notes. Two-tepaled female flowers are rare in Begonia sect. Petermannia , and there are only four species known to show this character state, namely B. willemii Ardi et al. from Sulawesi, B. fairchildii Ardi & D.C.Thomas from the Moluccas, and B. brangbosangensis Girm. and B. lombokensis Girm. from the Lesser Sunda Islands ( Girmansyah, 2016; Ardi et al., 2022). However, the new species can be easily distinguished from these species, as shown by the comparison in Table 1.

Additional specimens examined. INDONESIA. Sulawesi: SOUThEASTErn SUlAWESI: Kabaena Island, Batusangia peak, 3 viii 1993, McDonald & Ismail 4108 ( A, BO, K, L) ; 24 vi 2022, W. H. Ardi WI764 ( FIPIA) ; 29 xi 2022, Arman s.n. ( FIPIA) .

Figures

Figure 1. Begonia batusangiensis Ardi & D.C.Thomas, sp. nov. A, Habit; B, stipule; C, leaf lamina (abaxial surface); D, male inflorescence; E, bracts of male inflorescence; F, male flower; G, androecium; H, female flower (side view); I, female flower (front view); J, ovary (cross-section); K, fruit. Photographs: A–J (W.H. Ardi WI767), W. H. Ardi; K, Arman.

Figure 2. Begonia batusangiensis Ardi & D.C.Thomas, sp. nov. (A) and B. labengkiensis Ardi & D.C.Thomas, sp. nov. (B) in their natural habitats. Photographs: A (Arman s.n.), Arman; B (W.H.Ardi WI773), W. H. Ardi.

Figure 3. Map showing the distribution of Begonia batusangiensis, B. kabaenensis and B. labengkiensis.