A taxonomic study of the genus Phymaspermum (Anthemideae, Asteraceae)

M.Sc. (Botany)The subtribe Phymasperminae forms one of the six earliest diverging lineages within the tribe Anthemideae (Asteraceae/ Compositae). It comprises three genera, Eumorphia DC. (6 spp.), Gymnopentzia Benth. (1 sp.) and Phymaspermum Less. (ca. 19 spp.), all endemic to southern Africa. Generic and species delimitations and relationships within the subtribe are, however, uncertain. Anatomical, morphological and molecular characters are therefore explored in an attempt to resolve taxonomic delimitations and relationships within the subtribe. Two fruit characters, namely the presence of a papillose surface and more than 10 ribs are confirmed as synapomorphies for the subtribe. Phymaspermum is the largest and most complex genus within the subtribe and has been identified as one of the priority groups for taxonomic revision in South Africa. It is distinguished from the other two genera within Phymasperminae by the unique stalked myxogenic trichomes on the fruit surfaces. This character is shown to be a synapomorphy for Phymaspermum although subsequently lost in two species where it is replaced by resin canals in the fruit ribs. The species can be distinguished by a combination of habit, leaf, involucral and fruit characters. A taxonomic revision of Phymaspermum is presented, including comprehensive descriptions, a key to the species, nomenclature, typification, diagnostic characters with illustrations and maps with accurate geographical distribution data. Four new species are described, namely P. aphyllum, P. comptonii, P. oppositifolium and P. trifidum. Five previously recognised species, namely P. bolusii, P. montanum, P. equisetiodes, P. pubescens and P. villosum have been reduced to synonomy