The Amazonian monospecific genus Uleanthus is phylogenetically resolved in one of the most florally divergent clades of papilionoid legumes

Advances in molecular phylogenetic systematics have greatly improved our understanding of the evolutionary history and classification of numerous families of Amazonian flowering plants. Nevertheless, many significant components of Amazonian biodiversity remain insufficiently understood morphologically, biogeographically, and phylogenetically. This is the case of the monospecific genus Uleanthus (Papilionoideae, Leguminosae), which was traditionally classified as sister to the transcontinentally disjunct Angylocalyceae clade: one of the first-diverging lineages of papilionoid legumes. Here, we evaluate the phylogenetic placement of Uleanthus in a comprehensively sampled phylogenomic analysis combining plastome-wide and PCR-amplified matK sequence data. Additionally, we tested the placement of Uleanthus using a dataset of nuclear ribosomal ITS/5.8S and plastid trnL intron and matK sequences broadly sampled across the genistoid legumes. Our results shed light on the placement of Uleanthus, providing evidence of a close relationship between Uleanthus and the Colombian genus Orphanodendron: both forming a successive lineage to the African genus Camoensia. This previously unknown connection highlights an unanticipated evolutionary proximity among these genera despite their divergent floral morphologies. Given their placement among the main lineages of the large, quinolizidine-accumulating Genistoid s.l. clade, we propose their inclusion in an expanded Camoensieae clade. This recircumscription of a widely biogeographically disjunct Camoensieae also results in one of the most florally diverse clades of the Papilionoideae, whose constituent genera have not previously been taxonomically associated because of their largely contrasting floral architectures.