Taxonomic revision of African Psoralea pinnata species complex (Psoraleeae, Leguminosae)

Ambiguous species delimitations and nomenclature are a major impediment for users of biodiversity information. This is more pronounced in plant lineages that have experienced recent and rapid diversification or where there is a tendency to lump many species under a general name. The papilionoid genus Psoralea L. is a young lineage (Pliocene, ca. 75 species) which has diversified rapidly within the South African fynbos biome and adjacent habitats. All species bearing 5-19 foliolate leaves were previously often lumped within the polymorphic species Psoralea pinnata, resulting in an unwieldy complex of at least 28 taxa, of which only eleven species are formally named. In this study we analyzed live specimens and populations in the field and herbarium collections, capturing their morphological and geographic diversity, for species delimitation. The results support the recognition of 25 distinct species, of which 14 are described here as new: P. azuroides; P. brilliantissima; P. elegans; P. floccosa; P. imminens; P. intonsa; P. ivumba; P. kougaensis; P. montana; P. muirii; P. rhizotoma; P. semota; P. sordida; and P. suaveolens. The taxon P. pinnata var. latifolia Harv. is raised to species rank, as P. latifolia comb. nov. The name P. pinnata sensu stricto is restricted here to a taxon with 5-9-leaflets extending from the Cape Peninsula to the Kogelberg mountains. We provide a key for the identification of all 25 species along with full descriptions, distribution maps and notes on their conservation status.