Begonia capituliformis 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 : 10-11

2. Begonia capituliformis Irmsch. [§ Petermannia ], Bot. Jahrb. Syst. 50: 354 (1913).

– Type: Indonesia, Sulawesi, Minahasa, Bojong, O. Warburg 15190 (holotype B [B100238013], isotype B [B100238014]) .

Distribution. Indonesia: endemic to Sulawesi, North Sulawesi province (eastern North biogeographical region), Gunung Ambang, Gunung Lolombulan and Gunung Klabat (see Figure 2 ).

Habitat. Growing terrestrially in hill and upland forests at 600–900 m elevation.

Proposed IUCN conservation category. Endangered (EN), B1ab(iii)+B2ab(iii). This species is known from only a few collections from secondary forest at the periphery of the Gunung Ambang Nature Reserve, Gunung Lolombulan and Gunung Klabat. The collection localities are in forest patches close to human habitation and surrounded by land used for agricultural purposes (e.g. clove plantations) and other severely disturbed forest vegetation. Exploration of various hill forest localities on Gunung Klabat has not resulted in any additional collections, and therefore we must assume, until more extensive collection efforts reveal otherwise, that this species has a very restricted range. Because of its small extent of occurrence (EOO) (1344 km 2) and area of occupancy (AOO) (12 km 2), in combination with observed disturbance and loss of forest habitat at the border of the Gunung Lolombulan and Gunung Ambang Nature Reserve, we assess this species as Endangered ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimens examined. INDONESIA. Sulawesi. Northern arm of Sulawesi. Eastern North Sulawesi: Mount Lolombulan, Above Boyong atas, 24 ii 2008, J. Kinho & A.D. Poulsen 169 ( BO, E) ; Gunung Ambang , 22 ii 2008, M. Ardiyani, A.D. Poulsen & Ale 107 ( BO, E) ; N.E. Celebes, 29 vi 1956, L.L. Forman 314 (K) ; Wiau Complex, G. Klabat , 30 vi 1956, L.L. Forman 344a,b (K) .

Begonia capituliformis is endemic to the northern arm of Sulawesi. The species is characterised by a dense and strongly compressed subumbellate male inflorescence. This is a unique character among all member of Sulawesi Begonia sect. Petermannia but has some similarity to the inflorescence architecture of B. johntania Ardi & D.C.Thomas from North Konawe, Southeast Sulawesi, which is also in Begonia sect. Petermannia . However, the axis of the male inflorescence of the latter species is less compressed, the pedicels of the female flower are substantially longer, and the fruit are pendulous ( Ardi et al., 2018).

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).