Taxonomy of the Genus Phymaspermum (Asteraceae, Anthemideae)

Phymaspermum, the largest and most complex genus within the subtribe Phymasperminae, is revised and 17 species are recognised, all endemic to southern Africa. Four new species are described (P. aphyllum, P. comptonii, P. oppositifolium, and P. trifidum), five species are reduced into synonomy (P. bolusii, P. equisetoides, P. montanum, P. pubescens, and P. villosum) and P. thymelaeoides is recognized as the oldest available epithet for P. schroeteri. The species of Phymaspermum can be distinguished by a combination of habit, leaf, involucral, and fruit characters. Species relationships are assessed in a cladistic analysis of 12 anatomical and morphological characters. Phymaspermum is distinguished from Eumorphia and Gymnopentzia by the unique stalked myxogenic trichomes on the fruit surface. This character is shown to be a synapomorphy for Phymaspermum although subsequently lost in two species and replaced by resin canals in the fruit ribs. A comprehensive taxonomic treatment is presented, including a key to the species, correct nomenclature, typification, descriptions, and geographical distributions.