Mitogenomic data resolve basal relationships among passeriform and passeridan birds

Passerine birds compose over half of avian species diversity and exhibit an impressive array of phenotypic variation of interest to evolutionary biologists. Although this group has long been the focus of comparative study, many phylogenetic relationships within the group remain unresolved, despite an impressive number of molecular phylogenetic studies. Much of this uncertainty involves "transitional" groups potentially related to the ancestrally Australasian "core Corvoidea" and the primarily extra-Australasian Passerida, as well as basal relationships among Passerida. In this study data from mitochondrial genome sequences (mitogenomes) are brought to bear on higher-level passerine relationships. This paper reports analyses of new mitogenomes from 15 taxa carefully selected to address basal passeridan relationships, along with 110 previously-published passerine mitogenomes (most deriving from two intra-familial studies). These data corroborate many relationships previously established by multilocus nuclear data, as well as resolving several novel clades, including basal relationships of Passerida and relationships of that clade to several "transitional" forms. Although passerine mitogenomes pose significant analytical challenges (most notably substitutional saturation and base compositional heterogeneity), they appear to retain important information that should contribute to current and future understanding of passerine phylogeny.