By Luvo Magoswana
Othonna L. (Asteraceae: Senecioneae: Othonninae) is a genus of some 120 species concentrated in the Greater Cape Floristic Region (GCFR) of South Africa, with a few species extending into southern Namibia, Angola and Zimbabwe. The South African species of Othonna were last revised more than a century ago and many species, particularly in the winter rainfall-region, remain poorly understood. This study focussed on the geophytic species comprising the O. bulbosa group, distinguished by their tuberous rootstock and annual, leafy, aerial stems.
A comprehensive taxonomic treatment is presented, including descriptions, complete nomenclature and typification, illustrations and geographical distribution. Twenty-five species are recognised, of which four are newly described, and 17 names are reduced to synonymy. The species differ in habit, shape and incision of foliage, capitulum type (radiate vs. disciform), number of involucral bracts, pappus length, and cypselas (myxogenic vs. non-myxogenic). We place the species into four morphologically diagnosable series based on habit and capitulum type.
Othonna species, Left: Othonna gymnodiscus Brandvlei, middle: Othonna heterophylla Elandsberg, Right: Othonna intermedia Moedverloor
This work was part of SANBI staff member Luvo Magoswana’s MSc, which was awarded in March 2018.