Taxonomy, Taxa Richness, and Distribution of the Tribes Astragaleae, Crotalarieae, Genisteae, Indigofereae, and Loteae (Fabaceae) in Northeastern Mexico

Abstract

Background: The species richness and endemism of the species of the tribes Astragaleae, Crotalarieae, Genisteae, Indigofereae, and Loteae in northeastern Mexico are poorly documented and the systematics of these groups in the study area have not been updated according to the new taxonomic modifications proposed by the LPWG. Objective: Our objective is to update the taxonomy and to document the richness and endemism of legumes of the tribes Astragaleae, Crotalarieae, Genisteae, Indigoferae, and Loteae distributed in northeastern Mexico. Methods: This work is based primarily on fieldwork conducted by some of the authors over the past 40 years, and on the review of botanical specimens held in national and international herbaria. Results: Five tribes, eight genera, and 60 species of legumes were recorded and distributed as follows: Astragaleae, one genus (Astragalus), 29 species, and eight infraspecific categories; Crotalarieae, one genus (Crotalaria), 10 species, and three infraspecific categories; Genisteae, two genera (Lupinus and Spartium) and 11 species; Indigofereae, one genus (Indigofera), six species; Loteae, three genera (Acmispon, Coronilla, and Hosackia), and four species. Four introduced species were recorded: Coronilla varia, Crotalaria retusa var. retusa, Indigofera subulata var. scabra, and Spartium junceum, all of them with few records in the wild or cultivated as ornamentals, with no reports of weedy behavior or threats of population expansion. Twenty-nine species and two infraspecific categories are endemic to Mexico, of which 18 are exclusive to the northeastern region. Half and one-third of the recorded species are endemic to Mexico and northeastern Mexico, respectively, demonstrating their uniqueness and importance for conservation purposes. Astragalus and Lupinus constitute up to 95\% of the endemic species for the northeastern part of the country. The taxa richness of legumes in NE Mexico is unique, because almost half of them are endemic to the country and a third are endemic to this region, which requires the creation of appropriate measures for the conservation of the specific ecosystems where these species grow.