Taxonomic and nomenclatural updates in Calopogonium (Leguminosae: Papilionoideae) in South America

Calopogonium is included in the subtribe Glycininae of the tribe Phaseoleae and currently consists of eight species, most of which are restricted to the Neotropics. Calopogonium mucunoides is the only species with a pantropical distribution. The current circumscription of Calopogonium was proposed in a taxonomic study of the genus conducted by Carvalho-Okano in 1985. Since then, taxonomic studies on the genus have been largely regional, which has hindered the delimitation of some species and their differentiation from closely related taxa. To address this taxonomic impediment, a revision of South American species was carried out. Specimens were borrowed from, and visits made to, national and international herbaria. As a result, four species are recognized for South America, with the proposal to synonymize C. racemosum under C. galactioides. Furthermore, nomenclatural updates are proposed, including the lectotypification of 10 taxa and a neotypification for the type species of the genus, C. mucunoides. Conservation status was assessed for all species following IUCN criteria, with two species (C. caeruleum and C. mucunoides) classified as Least Concern (LC) and the other two species, C. galactioides and C. velutinum, classified as Near Threatened (NT). Additionally, we provide an identification key for the species of Calopogonium in South America, illustrative photographs, distributional maps, and remarks on nomenclature and taxonomy.