Phylogenetic analyses of Phaseolinae (Leguminosae) reveal a new genus endemic to limestone outcrops in Seasonally Dry Forests of Bahia, Brazil

Phaseolinae is one of the most diverse groups within the family Leguminosae, characterized by a style bearing a pollen brush and seeds with an epihilum. This subtribe has a complex taxonomic history and has undergone several changes over time. In the early 2000s, our research team found a phaseoloid liana growing in a limestone outcrop in western Bahia, Brazil. Its identity remained a mystery until recently, when we revisited the locality to study it in more detail and gathered material to generate nuclear ITS and plastid trnK/matK sequences. These sequences were included in a broadly sampled Phaseolinae matrix used to perform phylogenetic analyses and an ancestral character states reconstruction. Our results demonstrate that the enigmatic taxon represents a new lineage within subtribe Phaseolinae, sister to the genus Sigmoidotropis. This new lineage, along with Sigmoidotropis and Ancistrotropis, forms a clade here called the Sigmoid‐keel clade, since all representatives present flowers with sigmoid keel petals. The new taxon is here described as Delgadoa bambuicola gen. & sp. nov., a new genus and a new species of woody lianas known from only two localities in the state of Bahia. We also present an identification key to the genera of the Sigmoid‐keel clade, descriptions, illustrations, a distribution map, taxonomic comments, and a conservation status assessment of the new genus.