Refined generic and infrageneric classification of the Cape Psoraleeae clade (Fabaceae) – taxonomic studies in the phylogenomic era

The Cape Psoraleeae are a classic Cape clade, characterized by a recent diversification, and occurring in diverse habitats in the Greater Cape Floristic Region. Intensive taxonomic and phylogenetic studies in the past 20 years have contributed to the description of 48 species new to science, growing the genus to nearly 130 species, and changing generic classification. But there have been doubts on the taxonomic validity of two genera, Hallia and Otholobium, which had been previously recognized at genus level, but were synonymized under Psoralea following Sanger-based phylogenetic analyses. We use phylogenomic data, sampling over 70% of species in the Cape Psoraleeae, to infer phylogenetic relationships and monophyly of the genera. There is strong support for the backbone topology, which is resolved into three clades (core Psoralea incorporating Hallia pro parte, core Otholobium, and O. swartbergense and O. sericeum). We here refine the generic classification to recognize O. swartbergense/O. sericeum as a new genus Afrolobium, providing nomenclatural changes for the species; resuscitating Otholobium; and maintaining Hallia within Psoralea as a new subgenus. We further discuss trends in species discovery by discussing the placement of new species on the phylogenetic tree; most newly discovered species belong to the two largest clades and occur within the Greater Cape Floristic Region.