Taxonomic status of Myotis extremus (Chiroptera, Vespertilionidae) from Mesoamerica, with comments on the distribution and systematics of Myotis nigricans

Myotis nigricans was previously considered the most widely distributed Neotropical Myotis species, occurring from Mexico to northern Argentina, and several allopatric subspecies have been recognized, including M. n. extremus, from Mexico and Guatemala. However, recent studies have shown that M. nigricans is a species complex—many cryptic. Using molecular and morphological data, we assessed the taxonomic status of M. nigricans populations from Mexico, Guatemala, Paraguayan Chaco, and Brazilian Atlantic Forest. Our phylogenetic analysis indicated that M. nigricans is polyphyletic, and the populations classified as M. n. extremus were recovered in a clade composed of species from the ruber group. Populations from Paraguay and Brazil were recovered in distinct clades within the albescens group. Our morphological and morphometric analyzes corroborate the molecular findings, supporting the recognition of M. extremus as a full species. Furthermore, we propose that M. nigricans is a monotypic species occurring exclusively in the South American Atlantic Forest. Populations from other ecoregions should have their taxonomic status redefined in future studies.