Begonia carnosa (Teijsm. & Binn.) Teijsm. & Binn. [§ Petermannia

Ardi, W. H. & Thomas, D. C., 2022, SYNOPSIS OF BEGONIA (BEGONIACEAE) FROM THE NORTHERN ARM OF SULAWESI AND SANGIHE ISLAND, INDONESIA, INCLUDING THREE NEW SPECIES, Edinburgh Journal of Botany 79 (405), pp. 1-50 : 11-14

3. Begonia carnosa (Teijsm. & Binn.) Teijsm. & Binn. [§ Petermannia ], Epim. Ludg. Bat. 4 (1863).

Diploclinium carnosum Teijsm. & Binn., Tijdschr. Ned. - Indië 25: 420 (1863). –

Type: Indonesia, Sulawesi, Minahasa , Kapetaran , Teijsmann s.n. (lectotype K, designated here). Figure 3 .

Begonia heteroclinis Miq. ex J.J.Sm., Meded. Lands Plantentuin 19: 484 (1898); Koorders, Natuurw. Tijdschr. Ned.-Indië (1904). – Type: Indonesia, Sulawesi, de Vriese & Teijsmann s.n. (lectotype L [ L070107 ], designated here), syn. nov .

Perennial, monoecious herb with creeping stems, rooting at the nodes when in contact with the substrate, up to c. 20 cm tall, sparsely hairy with white hairs up to c. 1 mm long. Stem creeping, internodes 0.5–2 cm long, greenish or reddish. Leaves basifixed, alternate; stipules persistent, 5–6 × 3–5 mm, ovate, with an abaxially slightly prominent midrib projecting up to 3 mm at the apex, margin recurved in mature stipules, pinkish, glabrous; petioles 4.5–16 cm long, terrete, reddish, moderately hairy with white hairs up to 2 mm long; lamina 6.5–12 × 5–9 cm, asymmetrical, ovate to suborbicular, base cordate and lobes sometimes slightly overlapping, apex acuminate, margin entire to broadly dentate or sometimes shallowly lobed (up to 20% of leaf width), adaxial surface light green, glabrous, abaxial surface pale green, hairy on the veins, primary veins 6–8, actinodromous, secondary veins craspedodromous. Inflorescences: axillary, protogynous; female inflorescences 1- or 2-flowered, basal to male inflorescences, peduncles 1–5 cm long, pale green-reddish, glabrous, bracts persistent, ovate, 3–5 × 2–4 mm, pale green, translucent, glabrous; male inflorescences racemose-cymose (a thyrse), composed of up to 3 cymose partial inflorescences, branching dichasially or dichasially at the base and monochasially in distal part, each with 5–8 flowers, peduncles of partial inflorescences 2.5–7 cm long, pink-reddish, glabrous; bracts persistent, up to c.3 × 2 mm, ovate, pale green or creamy at base and reddish at the apex, midrib slightly prominent, apiculate. Male flowers: pedicels 13–16 mm long, white, glabrous; tepals 2, white, 7–12 × 9–14 mm, broadly ovate, base slightly cordate, margin entire, apex rounded; androecium of 19–21 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 3–10 mm long, reddish, glabrous; tepals 5, unequal, white, four larger 10–12 × 8–10 mm, ovate to broadly ovate, margin entire, apex rounded, one smaller, 8–10 × 4–6 mm, elliptic, margin entire, apex rounded; ovary (without wings) 7–9 × 4–5 mm, ellipsoid to narrowly obovoid, sometimes contorted, pale green, wings 3, subequal, base rounded, apex truncate, up to 6 mm long at the widest point (apically); style up to 4 mm long, basally fused, 3-branched, each stylodium bifurcate in the stigmatic region, stigmatic surface a spirally twisted papillose band, orange. Fruits: peduncle 1–5 cm long; pedicels 3–15 mm long; seed-bearing part 7–11 × 4–6 mm (excluding the wings), ovoid, sometimes slightly twisted, glabrescent, dehiscent, splitting along the wing attachment, wings subequal, base rounded, apex truncate, up to 8 mm long at the widest point (apically). Seeds barrel-shaped, c. 0.3 mm long.

Distribution. Indonesia: endemic to Sulawesi, North Sulawesi Province (eastern North biogeographical region), Kapetaran (Kapataran), Minahasa (see Figure 2 ).

Habitat. Lowland forest but also in village gardens, terrestrial in soil, in full shade, at c. 5 m elevation.

Proposed IUCN conservation category. Critically Endangered ( CR), B1 ab(iii)+B2ab(iii). This species is known from only two collections, namely the type specimen from Kapetaran (Kapataran), Minahasa , and the recently collected specimens from Tumpaan , South Minahasa, neither of which is from a legally protected area. The recent collection and further observations were made in a residential area in the Tumpaan district, which shows significant anthropogenic disturbance. Most lowland forest both in the Tumpaan district and in Kapetaran is in very poor condition or has been converted for agricultural use. Because of its very restricted known distribution and associated small EOO and AOO, and the observed and ongoing habitat disturbances and habitat loss in Kapetaran and Tumpaan, we assess this species as Critically Endangered ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimen examined. INDONESIA. Sulawesi. Northern arm of Sulawesi. Eastern North Sulawesi: Minahasa, Tumpaan District , 4 ii 2019, W.H. Ardi WI405 ( BO, KRB, SING) .

According to Teijsmann & Binnendijck (1863), Begonia carnosa was discovered in Kapetaran, Minahasa, Sulawesi. It can be recognised by a character combination including a recurved stipule margin; a reddish petiole, which is sparsely hairy with white, long, pilose hairs; ovate to suborbicular leaf laminas with dentate to broadly dentate or shallowly scalloped margin; a pseudoterminal male inflorescence, which has cymosely branching and subumbellate partial inflorescences; and female inflorescences or fruit with persistent bracts.

Despite the rather generic, relatively short, and incomplete description, which is missing several important characters such as the number of female flowers or fruits, the protologue is consistent with the morphology of a specimen that has been identified as Begonia carnosa but has a different locality ( Ternate, which Teijsmann and Binnendijck visited in March 1860 before traveling to North Sulawesi) indicated on the label (Teijsmann s.n., K). This specimen is the only material found in major herbarium collections that could potentially represent original material. It seems to be consistent with the recently collected material from Minahassa (WI405), and it is likely that the mismatch between the locality indicated in the protologue and the specimen label was the result of an error during specimen labelling. Therefore, we designate Teijsmann s.n. (K) as the lectotype of Begonia carnosa .

The name Begonia heteroclinis was ascribed to Miquel and the species was described in a publication by Koorders (1898: 484) explicitly stating that the description was written by J.J. Smith. Koorders (1898) mentions living material of this species cultivated at Bogor Botanic Gardens as well as original material by Miquel in the Herb. Hort. Bogor, but without providing any collector information. Corresponding herbarium voucher could not be located in the Herbarium Bogoriense (BO), however, and the only currently available potentially original material is Teijsmann & de Vriese s.n. (L0701077), a specimen in the Leiden herbarium labelled “ Begonia heteroclinis ” in Miquel’s handwriting. The specimen corresponds with the protologue, because it has a creeping stem with moderately long internodes, long petioles, ovate to suborbicular leaves, and female inflorescences or infructescences with two flowers or fruits. The specimen was collected when Teijsmann and de Vriese explored the Moluccas and Sulawesi. Therefore, we designate Teijsmann & de Vriese s.n. (L [L0701077]) here as the lectotype of Begonia heteroclinis .

Based on the newly available material from recent expeditions, including both herbarium specimens and cultivated plants in the living collections of the Bogor Botanic Gardens, a detailed description of the species could be completed and compared with the two original descriptions as well as with the illustrations in Koorders’ Flora van Celebes ( Koorders, 1898: 97). There are clearly strong similarities in crucial generative characters, such as male and female inflorescence architecture and fruit morphology, and also in some additional vegetative characters, such as the creeping stems with relatively long internodes (relatively rare character in Begonia sect. Petermannia ) as well as the petiole length and leaf shape. Based on these observations, we propose to reduce Begonia heteroclinis to a synonym of B. carnosa .

Figures

Figure 2. Distribution maps of Begonia species occurring on the northern arm of Sulawesi. Distribution points are from georeferenced collections from major herbarium collections (B, BO, E, K, KRB, L, SING), the Begonia Resource Centre (Hughes et al., 2015–) and the Sulawesi Begonia Data Portal (Thomas et al., 2013, continuously updated).

Figure 3. Begonia carnosa. A, Habit in situ; B, habit in cultivation; C, stipule; D, male inflorescence; E, female inflorescence; F, male flower (front view); G, female flower (front view); H, infructescence; I, fruit; J, ovary (cross-section of middle part). A–J from W.H. Ardi WI405. Photographs: W. H. Ardi.