Begonia cf. robusta Blume (1827: 96)

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 : 91

12. Begonia cf. robusta Blume (1827: 96)

Sect. Platycentrum

≡ Platycentrum robustum (Blume) Miquel (1856: 694)

≡ Casparya robusta (Blume) de Candolle (1864: 275) . Type:— not located.

= Begonia splendida Koch (1857: 74) . Type:— not located.

= Sphenanthera robusta Hassk. ex Klotzsch (1857: 182) . Type:— not located.

See Hughes (2008: 54) for more comprehensive synonymy and additional literature.

Additional literature:— Doorenbos (1980: 213); Tebbitt (2005: 204, pl. 163) [photo plate]; Hughes (2008: 54) [synonymy]; Thomas et al. 2011 [identification key].

Habitat:— In Sulawesi collected in primary upland to montane forests; on riverbanks and small islands in streams; at 1400 to 2530 m elevation.

Distribution: — Indonesia: Java, Bali, Sulawesi. In Sulawesi only known from Central Sulawesi (Sopu Valley, Mt. Gawalise) and Southern Sulawesi (Mt. Rantemario) ( Fig. 1B ).

Notes: — Several collections from Central and South Sulawesi belong to a species complex that includes Begonia robusta , Begonia multangula Blume (1827: 96) and several segregates from Bali and Lombok ( Tebbitt 2005; Girmansyah 2009; Hughes & Girmansyah 2011). According to Tebbitt (2005), typical Begonia robusta has adaxial leaf laminas with long red glandular hairs, the leaf margin is entire or has short rounded lobes, the infructescence peduncle is usually at least four times longer than pedicels, and the fruits have usually one longer wing and two shorter wings or ribs. In contrast to this, B. multangula has adaxial leaf laminas that are glabrous above or have short to long white or red glandular hairs, the leaf margin has several short angular lobes, the infructescence peduncle is usually less than three times as long as the pedicels, and the fruits have three equal ribs or short thickened wings ( Tebbitt 2005). However, Hughes (2008) and Hughes and Girmansyah (2009) emphasized there is a tendency to form hybrids in the wider group (fleshy-fruited species in section Platycentrum ) when species occur sympatrically, and that there are many morphologically intermediate specimens of possible hybrid origin (e.g. between Begonia multangula and B. robusta, Hughes 2008 ).

The material from Central and South Sulawesi shows fruits with two shorter and one larger wing, but the wings are not as well developed as in B. robusta from Java. The adaxial leaf surface shows a conspicuously reddish indumentum in the material from Central Sulawesi giving the surface a reddish shine as typical for B. robusta , but the adaxial leaf indumentum is whitish in the material from Southwest Sulawesi (there are red hairs along the stem). The peduncles of the infructescences are usually more than four times the length of the fruit pedicels in the Sulawesi material. The specimens from Central Sulawesi show a leaf margin that is irregularly lobed as in B. multangula , but leaf margins are only weakly lobed in the material from South Sulawesi. A close reexamination of the material from Sulawesi, the Lesser Sunda Isles and Java, as well as additional insights into introgression among the fleshy-fruited species in section Platycentrum are required to assess whether the material from Sulawesi should be separated as distinct species. As collections and morphological evidence are currently very limited, a wide species concept is adopted here and the Sulawesi material is identified as part of the B. robusta complex.

Provisional IUCN conservation assessment:— Least Concern (LC) (Hughes et al. 2008).

Additional specimens examined: — INDONESIA. Sulawesi, Central Sulawesi: Track between Sopu valley and Danau Tambing, 24 May 1979, van Balgooy 3486 (A, BO, K, L) . South Sulawesi: Gunung Rantemario , 24 Apr. 2009, D.C. Thomas & W.H. Ardi 09-80 ; ibid. 25 Apr. 2009, D.C. Thomas & W.H. Ardi 09-85 .

For specimens outside of Sulawesi, see Hughes (2008) and Hughes et al. (2015).

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.