Taxonomy, Taxa Richness, and Distribution of the Tribes Desmodieae, Millettieae, Psoraleeae, Robinieae, Sesbanieae, Sophoreae, and Trifolieae (Fabaceae) in Northeastern Mexico

Background: Although there is a compendium of species diversity for the Flora of North America, including the Fabaceae, many legume species were excluded. Therefore, this study fills this information gap and updates the systematics and nomenclature of this group in accordance with the new changes proposed by the LPWG. Objective: To update the taxonomy and to document the species richness and endemism of the tribes Desmodieae, Millettieae, Psoraleeae, Robinieae, Sesbanieae, Sophoreae, and Trifolieae (Fabaceae) in northeastern Mexico. Methods: The study is based primarily on the botanical specimens collected by some of the authors during the last 45 years and the review of national and international herbaria, where legumes from northeastern Mexico are deposited. Results: Richness—A total of 7 tribes, 22 genera, and 69 species of legumes were recorded, and distributed as follows: Desmodieae (four genera, 29 species; Millettieae, three genera, nine species); Psoraleeae (two genera, four species); Robinieae (five genera, eight species); Sesbanieae (one genus, two species); Sophoreae (four genera, seven species), and Trifolieae (three genera, nine species). Endemism—A total of 15 of the 69 species recorded in the northeastern region are endemic to Mexico (22%). Five of the seven tribes under study have endemic taxa in the northeastern part of the country: Desmodieae (two species), Robinieae (two species), Sophoreae (three species), and Trifolieae (one species). Desmodium is the genus with the highest number of endemic species (4), followed by Dermatophyllum with two species. Conclusions: The diversity of legume species in the studied tribes in northeastern Mexico is high; almost a quarter of the species studied are endemic to this region. Therefore, it is necessary and a priority to create policies and appropriate practical measures for the conservation of the ecosystems where these taxa thrive.