Begonia insularum Irmsch. [§ 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 : 23-25

9. Begonia insularum Irmsch. [§ Petermannia ], Bot. Jahrb. Syst. 50: 353 (1913).

– Type: Indonesia, Sulawesi, Sangir island , Warburg, O. 16107 (holotype B [B100238023]) . Figure 7 .

Distribution. Indonesia: endemic to Sulawesi, Sangihe (Sangir) Island (see Figure 2 ).

Habitat. Transition of upland to hill rain forest with palms or secondary forest at 800 m elevation.

Proposed IUCN conservation category. Vulnerable (VUD2). This species is known from only two collections, both of which have no exact locality information. Despite the legal protection of some areas on Sangihe (Sangir) Island due to being part of Sanger Gunung Api Uwu National Park, there are clear signs of anthropogenic disturbance, including habitation and nutmeg plantations, around the island. All available Begonia specimens from A, B, BM, BO, CEB, E, K, L and SING have been consulted, and therefore it must be assumed, at least until more intensive collecting on Sulawesi may reveal otherwise, that this species has a very restricted range. Therefore, this species is probably ‘prone to the effects of human activities or stochastic events within a very short time period in an uncertain future’ ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimen examined. INDONESIA. Sulawesi. Sangihe Talaud Islands: Sangihe Island , 5 xi 1998, D. Hicks & Anius 135 (K) .

Begonia insularum is endemic to Sangihe (Sangir) Island. It is one of the most poorly known species in Sulawesi, being known from only a few specimen records and observations. Recently, the species was documented during a field survey by a colleague from Bogor Botanic Gardens (Ully Rachmawaty); however, no herbarium vouchers were made. Begonia insularum is similar to B. isoptera Dryand. ex Sm. from western Malesia (Java and Sumatra), but B. insularum can be distinguished from that species by several characters, including fewer stamens (25 vs 40 stamens), 5-tepalled female flowers (vs 3-tepalled female flowers) and fruit wings with a rounded base and truncate apex (vs fruit wings with cuneate base and truncate apex).

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 7. Begonia insularum in its natural habitat, Sangihe Island. A, Habit; B, infructescence and male inflorescence. Photographs: Ullie Rachmawaty.