We sequenced 2005 bp of the mitochondrial ND2 and cytochrome b genes from the 25 recognized species of New World orioles (Icterus). Our data confirmed the monophyly of Icterus and produced a well-resolved phylogeny showing three main clades of orioles. We also sequenced multiple subspecies for most polytypic taxa. Our findings demonstrated the importance of dense taxon sampling below the species level in two ways. First, we found evidence that two species are polyphyletic, I. galbula (Northern oriole) and I. dominicensis (Black-cowled oriole). Choosing different subspecies from either of these taxa would lead to different species-level phylogenies. Second, adding subspecies even to monophyletic groups produced a bootstrap tree with significantly more support. Of the two genes that we used, ND2 provided more resolution than did cytochrome b. ND2 evolved up to 40% faster than cytochrome b, yet shows a higher saturation threshold. Our findings suggest that ND2 may be superior to cytochrome b for resolving species-level phylogenies in passerine birds.
Bibliographical noteFunding Information:
We thank the following institutions for loans of tissues: Academy of Natural Sciences Philadelphia; Field Museum of Natural History; Louisiana State University Museum of Zoology; Museu Paraense Emílio Goeldi, Belem, Brazil; Smithsonian Tropical Research Institute; University of Alaska Museum; Museo de Zoologia, Facultad de Ciencias, UNAM, Mexico, D. F.; and the University of Washington Burke Museum. Adolfo Navarro Siguenza, Octavio Rojas Soto, Blanca Hernandez, and Amadeo Estrada (all Museo de Zoologia, UNAM) all provided invaluable help with permits and collecting in Mexico. We also thank Biff Birmingham, Nedra Klein, Sievert Rohwer, P. William Smith, and Kevin Winker for assistance obtaining tissues. Kevin Johnson provided ND2 sequences for the outgroups and provided feedback throughout the project. Rachelle Blackwell, Cliff Cunningham, Shannon Hackett, John Klicka, Sonja Scheffer, Bob Zink, and two anonymous reviewers gave helpful suggestions regarding lab-work and other aspects of the project. Matt Etterson, Anne Kessen, and Bob Zink contributed helpful comments on earlier drafts of the manuscript. Rob Fleischer provided office space during the final writing of the manuscript. Initial phases of this research were supported by a National Science Foundation Grant to S. M. L. (BRS—8614240). K. E. O. was supported by a National Science Foundation Postdoctoral Fellowship in Biosciences Related to the Environment.