Comprehensive phylogenetic analysis of tribe Psoraleeae (Fabaceae) supports segregation of the South American Otholobium as a New Genus Grimolobium

Tribe Psoraleeae (Fabaceae) is a clade nested within the Millettioid/Phaseoloid legumes, yet set apart by its single-seeded fruit. With a cosmopolitan distribution, the tribe is currently recognized as having 10 genera: Bituminaria, Cullen, Hoita, Kartalinia, Ladeania, Orbexilum, Otholobium, Pediomelum, Psoralea, and Rupertia. Several previous molecular systematic works have shown the non-monophyly of species within Otholobium, with lineages separating geographically between members distributed in South America vs. Africa. However, previous sampling was sparse regarding species sampled from South America. Here, we increase our sampling of South American Otholobium species and estimate phylogenies based on four DNA regions (ITS, rpoB-trnC, trnS-trnG, trnL-trnF) to provide conclusive evidence that South American species of Otholobium should be segregated and recognized as a new genus, Grimolobium A.N.Egan, C.H.Stirt. & A.Bello, chosen to honour the work of James Grimes, a botanist whose seminal work on New World Psoraleeae improved the taxonomic evolutionary understanding of this plant group. We describe this new genus based on a new phylogenetic analysis of the tribe Psoraleeae and our exploration of morphology within this phylogenetic context and provide the necessary new combinations and keys.