A Taxonomic Revision of the Argyrolobium robustum and A. transvaalense Groups (Fabaceae) in Southern Africa

Abstract

Abstract— Previous studies on the genus Argyrolobium (Genisteae, Fabaceae) in southern Africa recognized a group of species defined by a suffrutescent habit, monomorphic flowers and leaves, and the plants not turning black when dried as ‘section A. transvaalense.’ A formal rank was never published for this group. Here a taxonomic study of this group is conducted, including comprehensive descriptions and a key to the species, nomenclature, typifications, diagnostic characters, and geographical distribution. Based on an assessment of morphological characters, two groups can be recognised: 1) the A. robustum group that comprises four species with a herbaceous habit with up to 55-flowered inflorescences, flowers drying black or turning black when damaged, keel petals lacking pockets, and staminal sheaths fully open above, and 2) the A. transvaalense group comprising five species with a suffruticose habit with up to 24-flowered inflorescences, flowers becoming discoloured (darker coloured or brown) when dried, keel petals with pockets except in A. megarhizum, and staminal sheaths variously fused into a closed tube.