Begonia sect. Oligandrae M.Hughes & W.N.Takeuchi, 2015

Hughes, Mark & Takeuchi, Wayne, 2015, A new section (Begonia sect. Oligandrae sect. nov.) and a new species (Begonia pentandra sp. nov.) in Begoniaceae from New Guinea, Phytotaxa 197 (1), pp. 37-44 : 38

Begonia sect. Oligandrae M.Hughes & W.N.Takeuchi , sect. nov.

Type: — Begonia oligandra .

Low growing caulescent herbs, monoecious; stems repent or suberect and adventitiously rooting at the nodes. Leaves alternate, ovate to lanceolate, finely divided or entire. Inflorescences terminal or axillary, cymose, bracts conspicuous, usually persistent, white or pink. Male flowers basal, tepals 3–4, in unequal pairs or one tepal reduced, free, white, stamens 4–8, free, androecium symmetric. Female flowers solitary, terminal, tepals 3–4, in unequal pairs or one tepal reduced, free, white or pink, styles bifid and branched or capitate and cylindrical, not spirally twisted. Fruit 3-locular, placentae axillary, bifid; wings 3, unequal (1+2), fleshy and horn-like, the larger wing extended apically towards the tepals, smaller wings rounded.

Species list: —Five species. Begonia brassii , B. chambersiae , B. oligandra , B. pentandra sp. nov. and B. sandsiana .

Distribution: —In montane forests of the New Guinea Highlands, from 900–2300 m, sometimes on karst limestone.

Etymology: —The epithet is from the Greek oligo (few) and andro (male), referring to the small number of stamens.

Taxonomic notes: —The affinities of Begonia sect. Oligandrae are difficult to ascertain, primarily because the reproductive structures are unusual and highly modified. Reduced stamen number and showy bracts are similarly found in Begonia sect. Symbegonia ( Warburg 1894: 149) Forrest & Hollingsworth (2003: 208) endemic to New Guinea and possibly the closest relative to the new section. However sect. Symbegonia differs (corresponding characters for sect. Oligandrae in parentheses) in usually having solitary-axillary female flowers (female flowers inserted at the apex of a male cymose inflorescence in B. pentandra and B. chambersiae ), fused female tepals (free female tepals), noticeably enlarged receptacles (planate or slightly rounded receptacles), and elongated stigmas (stigmas inconspicuous or capitate). Repeated attempts at DNA-sequencing from silica dried leaves of B. sandsiana and B. pentandra were unsuccessful, hence the phylogenetic relationship of the new section remains unknown.