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

We assessed levels of genetic differentiation based on mitochondrial DNA se quences (portions of the cytochrome-b and ND2 genes) at several taxonomic l evels in thamnophilid antbirds. Our focus was to investigate genetic differ entiation among populations of two species in the genus Drymophila and to i dentify the sister genus to Drymophila. In addition, we present evidence of high levels of population subdivision in Hypocnemis cantator (Warbling Ant bird). 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, ofte n exceeded 2% between populations. Divergences within H. cantator, a specie s with more generalized habitat requirements and a more "continuous" distri bution, were even higher, including 5.7% divergence between samples separat ed by 350 km of apparently continuous Amazonian forest. At higher taxonomic levels, genetic distances suggest that antbird genera and biological speci es are old. Genetic divergence between the two species that comprise the ge nus 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 n ot monophyletic, supporting previous allozyme analyses. In addition to the protein-coding sequences, we found that spacer regions between genes also p rovided phylogenetically informative characters from the level of suboscine families to within the biological species that we studied.