Systematics of three Amazonian antwren groups (Aves: Passeriformes: Thamnophilidae: Myrmotherula and Isleria)

Working within the framework of a companion phylogenetic analysis, we reexamined species limits within three lineages of antwrens (two species and one species complex) widely distributed across the Amazon Basin. Diagnostic differences in vocal and plumage characters provided the basis for the following taxonomic revisions. Myrmotherula longipennis is found to comprise three species: (1) M. longipennis (sensu stricto), which is confined to the region north of the Amazon; (2) M. garbei, which is elevated from subspecies status and includes the subspecies zimmeri; and (3) M. paraensis, which is also elevated from subspecies status and includes subspecies transitiva and ochrogyna. Myrmotherula menetriesii also comprises three species: (1) M. menetriesii (sensu stricto), which occurs in the southwest quadrant of Amazonia and includes the subspecies berlepschi; (2) M. cinereiventris, which is elevated from subspecies status and includes the subspecies pallida; and (3) M. omissa, which is monotypic and is also elevated from subspecies status. We maintain two species in the Isleria complex, I. guttata and I. hauxwelli. Isleria guttata remains monotypic, but the subspecies of I. hauxwelli are revised. Isleria h. hellmayri is preserved as currently defined, but I. h. suffusa is synonymized with the nominate form, the geographic range of which is restricted to western Amazonia. A fourth subspecies, I. h. clarior, is resurrected; this subspecies occupies the major part of the range previously assigned to I. h. hauxwelli.