Abstract
Morphological, vocal and genetic studies have shown that the Madeira River and its right bank tributaries delimit populations of primates and birds. We sequenced the cytochrome b gene (approx. 950 bp) for individuals of three suboscine passerine bird species, Glyphorynchus spirurus (Furnariidae), Willisornis poecilinotus (Thamnophilidae) and Schiffornis turdina (Tityridae), on opposite banks of the Madeira River and two of its right-bank tributaries, the Aripuana and Jiparana rivers. Phylogenetic hypotheses (parsimony, maximum likelihood and Bayesian analysis) revealed clades that have over 3.1% genetic differentiation on opposite banks of the Madeira River for G. spirurus, W. poecilinotus and S. turdina, suggesting that this river restricts gene flow among populations of these three species. The Jiparana and Aripuana rivers apparently separate distinct populations of G. spirurus, the smallest species we examined, but not those of the other two heavier bodied species, W. poecilinotus and S. turdina. In G. spirurus four clades with high levels of genetic differentiation (3.2–5.5%) were found to be delimited by the three rivers evaluated, whereas in W. poecilinotus and S. turdina no genetic structure across the Jiparana and Aripuana rivers was detected. In general, birds that are known to show population structure across the Madeira tributaries (Glyphorynchus spirurus, Hemitriccus minor, Hypocnemis rondoni, Herpsilochmus stotzi, and Hylophylax naevius) have body masses smaller than those of both Willisornis poecilinotus and Schiffornis turdina, but some exceptions are discussed. Future studies controlling for several variables are necessary to determine the extent to which body mass is a useful predictor of genetic population structure in understory suboscine passerines.
Highlights
Avian distribution patterns are reasonably well known and influential in studies of evolutionary processes
Phylogenetic hypotheses revealed clades that have over 3.1% genetic differentiation on opposite banks of the Madeira River for G. spirurus, W. poecilinotus and S. turdina, suggesting that this river restricts gene flow among populations of these three species
We studied three species of passerine birds belonging to three different families: Glyphorynchus spirurus (Furnariidae), Willisornis poecilinotus (Thamnophilidae), and Schiffornis turdina (Tityridae)
Summary
Avian distribution patterns are reasonably well known and influential in studies of evolutionary processes. Jürgen Haffer was one of the first authors to compile bird distribution data to describe biogeographic patterns in South America (Haffer 1974). His work made a great contribution to evolutionary studies and to the formulation of speciation hypotheses in Amazonia. The “centres of species endemism” he described remain largely unchanged in analyses of distribution patterns for many avian groups. They have been generally accepted in subsequent works, and in the Amazon basin these regions are often delimited by large rivers (Haffer 1974; Cracraft 1985; da Silva & Oren 1996). Similar patterns are found in other Amazonian vertebrate taxa, including primates and butterflies (Wallace 1852; van Roosmalen et al 1998; Hall & Harvey 2002), suggesting that rivers are important barriers to dispersal
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