Begonia (sect. Cyathocnemis) A. DC.

Begonia sect. Cyathocnemis (Klotzsch) A.DC.

Prodromus Systematis Naturalis Regni Vegetabilis 15 (1): 332 (de Candolle 1864). – Cyathocnemis Klotzsch, Gattungen und Arten 1854: 247 (Klotzsch 1855).

– Type: holotype: Cyathocnemis obliqua Klotzsch = Begonia cyathophora Poepp. & Endl.

Synonymy notes

For a full list of sectional synonyms, see Moonlight et al. (2018).

Notes

This section was first described as a genus by Klotzsch (1855: 220) to include his Cyathocnemis obliqua Klotzsch nom superfl., which had two staminate tepals, two pistillate tepals, and bifid placentae. Alphonse Pyramus de Candolle (1864: 122) later treated this genus as a section with a single species, B. cyathophora, separated from B. sect. Ruizopavonia by its fused bracts. Doorenbos et al. (1998) had a different concept of the section, which they delimited to include seventeen species with transversely ovate leaves, while B. sect. Ruizopavonia included species with straight leaves. Doorenbos et al. ’s (1998) concept of the section included for the first time several species with five tepals on the pistillate flowers and species lacking fused bracts. Moonlight et al. (2018) largely followed this circumscription, but included one species and excluded another based upon phylogenetic evidence. This later circumscription is similar to Doorenbos et al. ’s (1998) but the two sections are now better distinguished by their venation rather than their leaf shape: B. sect. Cyathocnemis now includes species with palmate or palmate-pinnate venation, while B. sect. Ruizopavonia includes species with pinnate venation.

While the distinction between B. sect. Cyathocnemis and B. sect. Ruizopavonia is mostly clear (though see notes under B. sect. Ruizopavonia), it is more difficult to distinguish the section from members of B. sect. Hydristyles. Doorenbos et al. (1998) distinguished this section by its irregularly multifid styles but Moonlight et al. (2018) and Moonlight & Reynel (2018) have since included two species with multifid styles in B. sect. Cyathocnemis, with their placements supported by molecular evidence. Begonia sect. Hydristyles, however, remains poorly sampled in molecular analyses and poorly known morphologically so it remains to be seen whether it is a natural group and if so, how it should be defined.

The centre of diversity for B. sect. Cyathocnemis is Peru, where 17 of the 20 species assigned with confidence to the section are found (with four non-Peruvian species being tentatively assigned to the section; Moonlight et al. 2018). This treatment therefore represents a revision of most of the section and the species concepts we present here are significantly different to those of previous floristic accounts. We describe five new species in addition to two described by Moonlight & Reynel (2018) and describe a sixth, B. imbrexiformis Moonlight sp. nov., but only tentatively assign it to the section (see notes under B. imbrexiformis sp. nov.). Finally, we propose five new synonyms within a much-expanded concept of B. bracteosa.