Integrative revision of species limits in the genus Schiffornis (Aves: Tityridae) reveals cryptic diversity in the Neotropics

Abstract

Abstract Accurate species delimitation is essential for many biological subdisciplines. Nonetheless, current species diversity remains incompletely documented even in well-studied groups such as birds. Here, we take an integrative approach to examine species limits in the genus Schiffornis, a widespread group of dull-plumaged, whistle-voiced suboscine passerines of Neotropical humid-forest understory, currently considered to comprise seven species. We measured geographic variation in song, morphology, and mitochondrial and genome-wide nuclear markers to resolve the taxonomy of the genus. We show that Schiffornis comprises 13 separately evolving population lineages, of which most qualify as species taxa under all species definitions. These include a cryptic new species, several species splits, and the resurrection of a morphologically undifferentiated, but vocally and genetically distinct, taxon that was synonymized nearly a century ago in the Schiffornis turdina complex. We also found several hitherto unnoticed contact zones between diverging lineages and a leapfrog pattern of geographic song variation in the S. turdina complex, and we highlight potential avenues of further research of this genus.