Underestimated endemic species diversity in the dry inter‐Andean valley of the Río Marañón, northern Peru: An example from Mimosa (Leguminosae, Mimosoideae)

Abstract Molecular phylogenies which include multiple accessions of species and near complete taxon sampling can be an important tool for estimating species diversity when used in combination with traditional morphology‐based taxonomy. Here we use a densely sampled plastid gene tree for a morphologically complex group within the legume genus Mimosa (sect. Batocaulon ser. Andinae ) to improve estimates of species limits and diversity in the poorly known dry inter‐Andean valley of the Río Marañón, northern Peru. Based on the plastid gene tree, Mimosa ser. Andinae , which previously comprised four species, is re‐circumscribed to include six Andean dry‐forest species from northern Peru, Ecuador and southern Colombia, including the new species, M. jaenensis , described here. A further three candidate species are identified within the section based on high levels of sequence variation among accessions. With the additional species, the Marañón valley is now known to harbour nine narrowly restricted endemic species of Mimosa , a pattern of multiple congeneric endemics mirrored in many other plant genera as well as several animal groups. Our results, in combination with other published studies, suggest that overall species diversity in the Marañón has been significantly under‐estimated. Further work is needed to identify conservation priority areas in the Marañón in order to protect its unique flora.