Taxonomic revision of the Pteronia uncinata group (Asteraceae: Astereae) and the resurrection of Pteronia trigona

Pteronia L. is a southern African endemic genus, mostly diversified in the Greater Cape Floristic Region. The genus was identified as one of the taxonomic priorities in South Africa. This study presents a taxonomic treatment of an informal morphological group: the Pteronia uncinata group. Five species are here recognised (P. diosmifolia Brusse, P. fasciculata L.f., P. paniculata Thunb., P. teretifolia (Thunb.) Fourc. and P. uncinata DC.). They are readily distinguished from congeners by the densely clustered terminal capitula often arranged in a compound corymb. Taxonomic descriptions, diagnostic characteristics, geographical distributions and ecological information, as well as an identification key to the five species recognised within the P. uncinata group are provided. Pteronia trigona E.Phillips had, until now, been considered a synonym of P. teretifolia but differs from the latter species (and the other species within the P. uncinata group) by the solitary, sessile capitula. As a result, Pteronia trigona is here resurrected for a taxon from the Eastern Cape, South Africa. Although P. trigona is not considered to form part of the P. uncinata group, a taxonomic description to clarify its identity is provided and the nomenclature, distribution and ecology for this species provided.