DNA sequence data often appear to contradict low-level avian taxonomy, which is usually based on patterns of external phenotypic similarity. We examined such an apparent contradiction in the Nearctic rosy-finches. On the basis of several phenotypic characters the finches were divided into three species congeneric with three Asian species. When Nearctic taxa were analyzed in a principal components analysis, 66.9% of phenotypic variation was explained by differences between the Bering Sea and continental populations, sexual dimorphism and a latitudinal cline. Our phylogenetic analysis of mitochondrial ND2 sequences revealed four clades among six species of rosy-finches. Three clades corresponded to three Asian species. The fourth clade included all three Nearctic species. Their haplotypes were not reciprocally monophyletic and the combined genetic variability of all Nearctic taxa was lower than in two of their Asian congeners. A Z-specific intron (ACO1I9) and an autosomal coding locus (MC1R) provided little additional phylogenetic information, most likely because of the longer coalescence times relative to ND2. Phylogeographic analyses of ND2 data revealed significant gene flow among neighboring localities regardless of their taxonomic assignment. Our analyses showed that DNA and phenotypic data are not in conflict, but rather complement each other, and together help clarify species limits. Our data are consistent with a single species in North America, not three.
Bibliographical noteFunding Information:
Tissue samples for this study were provided by the University of Washington Burke Museum, the Museum of Natural History, Louisiana State University, National Museum of Natural History, Smithsonian Institution, the Museum of Vertebrate Zoology, University of California, Berkeley, the Zoological Museum of Moscow State University, University of Alaska Museum of the North, University of Alaska Anchorage Avian Collection, and the American Museum of Natural History. Five anonymous reviewers provided constructive criticism of the manuscript. We are grateful to all these institutions and individuals. This project was supported by the Department of Ecology, Evolution and Behavior, University of Minnesota, and NSF grant DEB 9707496 to RMZ. Appendix A
- Gene flow
- Geographic cline
- Nuclear DNA
- Species limits