Phylogenetic relationships within Passerida (Aves: Passeriformes): a review and a new molecular phylogeny based on three nuclear intron markers

The avian clade Passerida was first identified based on DNA-DNA hybridization data [C.G. Sibley, J.E. Ahlquist, Phylogeny and Classification of Birds, 1990, Yale University Press, New Haven, CT]. Monophyly of the Passerida, with the exception of a few taxa, has later been corroborated in several studies; however, the basal phylogenetic relationships have remained poorly understood. In this paper, we review the current knowledge of the phylogenetic relationships within Passerida and present a new phylogeny based on three nuclear introns (myoglobin intron 2, ornithine decarboxylase introns 6 and 7, as well as beta-fibrinogen intron 5). Our findings corroborate recent molecular hypotheses, but also identify several hitherto unrecognized relationships.