Taxonomy of the southern African Psoralea aphylla complex (Psoraleeae, Leguminosae)

Abstract

The genus Psoralea L., comprising about 70 species, has its centre of diversity and endemism in the Greater Cape Floristic Region of South Africa. Species delimitation and identification in the genus are difficult. Many putative species are unpublished or known only by manuscript names. As a first step to address this problem this study reports on the taxonomy of the Psoralea aphylla complex - a distinct group of species characterised by either a complete absence of leaves, a reduction of the leaves into scales, or the occurrence of small filiform leaflets. Plants may be suffrutices, small to large shrubs, or trees. Morphological and ecological analyses of herbarium specimens and recent field collections distinguished ten species within the complex. Three species (P. aphylla L., P. filifolia Eckl. & Zeyh. and P. peratica C.H.Stirt.) are already published, while the seven other taxa have been known by manuscript names and are formalised in this paper (P. congesta C.H.Stirt. & Muasya; P. fleta C.H.Stirt.; P. gigantea Dludlu, Muasya & C.H.Stirt.; P. pullata C.H.Stirt.; P. ramulosa C.H.Stirt.; P. rigidula C.H.Stirt.; and P. usitata C.H.Stirt.). We provide a key for the identification of all ten species along with full descriptions, illustrations, distribution maps and some notes on the conservation statuses of the species. aphylla complex.