A taxonomic revision of the Pteronia camphorate group (Astereae, Asteraceae)

Abstract

As a first step towards a comprehensive revision of Pteronia (Asteraceae, Astereae), we present here a taxonomic treatment of the Pteronia camphorata group, in which we recognise three species. The group includes the type species P. camphorata (an important medicinal plant) and is easily distinguished from the rest of the genus by the glabrous rather than glandular or variously pilose cypselas. The lectotype of P. camphorata has involucral bracts with entire margins and long acuminate apices, both diagnostic characters for P. stricta. As such P. stricta is here reduced into synonymy with P. camphorata and the next available name, P. aspera Thunb, reinstated to accommodate the species heretofore treated as P. camphorata. Three varieties within Pteronia camphorata had been previously recognised (var. armata, var. laevigata and var. longifolia). The characters distinguishing var. armata were found to be continuous with the variation observed within var. longifolia. The third infraspecific taxon, var. laevigata, was however found to be distinct and is therefore recognised here as a new species, P. cederbergensis Bello, Magee & Boatwr. It is readily distinguished by the glabrous branches, opposite to sub-opposite somewhat succulent leaves, the 2-seriate pappus and larger, obclavate cypselas. Transverse sections of the leaves and cypselas were also examined and provide additional differences between the three recognised species.