Avian mitochondrial DNA sequence divergence across a headwater stream of the Rio Tapajos, a major Amazonian river

Populations of ten Amazonian bird species were sampled on opposite banks of the Rio Teles Pires, a headwater stream of the Rio Tapajos, in the Alta Floresta region, northern Mato Grosso, Brazil. The river is 100-300 in wide in this region. We found a range of genetic differentiation from none to relatively high levels; six of the ten species studied exhibit what appear to be genetic breaks at the river. With one exception, the antbird Hylophylax poecilinota, there is no morphologically recognized differentiation correlating with genetic differentiation. From the perspective of traditional morphology-based taxonomy, the Rio Teles Pires is not a faunal barrier. Rather, contact zones between members of species and subspecies pairs appear more or less randomly distributed in this region, some being located at varying distances to the cast, others at varying distances to the west of the Rio Teles Pires, with few following the course of this river itself.