| Unfragmented, biophysically complex river networks are rare, but their study is vital to understanding the processes by which imperiled, diverse riverine organisms are sustained. In
such a network, we studied the increased biophysical heterogeneity that can occur when multiple
tributaries enter a mainstem in close proximity, and used an iterative, aggregation analysis to investigate its effect on biodiversity and food-web characteristics that may be linked to its maintenance. We measured habitat, surveyed fishes and amphibians, sampled their gut contents, and collected organism tissues for stable isotope analyses. Our analyses revealed increased habitat heterogeneity, fish and amphibian diversity, and meta-food web complexity associated with combinations of tributary confluences, and we observed as much variation in diets of ecospecies among habitats as among all the assemblage within a habitat, pointing to high feeding
plasticity. Such trophic and associated meta-food web complexity may be important to biodiversity maintenance in river networks. |