High levels of mitochondrial DNA differentiation in two lineages of antbirds (Drymophila and Hypocnemis)

We assessed levels of genetic differentiation based on mitochondrial DNA sequences (portions of the cytochrome-b and ND2 genes) at several taxonomic levels in thamnophilid antbirds. Our focus was to investigate genetic differentiation among populations of two species in the genus Drymophila and to identify the sister genus to Drymophila. In addition, we present evidence of high levels of population subdivision in Hypocnemis cantator (Warbling Antbird). This widespread Amazonian taxon co-occurs, on a local scale, with D. devillei (Striated Antbird). Sequence divergences among populations of D. devillei and D. caudata (Long-tailed Antbird), two bamboo-specialists, often exceeded 2% between populations. Divergences within H. cantator, a species with more generalized habitat requirements and a more "continuous" distribution, were even higher, including 5.7% divergence between samples separated by 350 km of apparently continuous Amazonian forest. At higher taxonomic levels, genetic distances suggest that antbird genera and biological species are old. Genetic divergence between the two species that comprise the genus Hypocnemis was 9.3%, and divergence between D. devillei and D. caudata averaged 7.2%. Weighted parsimony and maximum-likelihood analyses supported Hypocnemis as the sister taxon to Drymophila; the genus Myrmotherula was not monophyletic, supporting previous allozyme analyses. In addition to the protein-coding sequences, we found that spacer regions between genes also provided phylogenetically informative characters from the level of suboscine families to within the biological species that we studied.