Trophic Basis of Production in a Neotropical Headwater Stream: Implications for the Ecological Consequences of Amphibian Declines

The lack of a conceptual model describing the structure and function of neotropical streams limits our understanding of the potential consequences of ongoing amphibian declines in these systems. We examined gut contents of dominant invertebrates and tadpoles in a Panamanian headwater stream and combined this information with secondary production estimates to assess the trophic basis of production (TBP) and energy flow pathways. Omnivory was prevalent among all taxa examined. Non-algal biofilm material was the major contributor (average = 52%) to production of dominant taxa of all functional feeding groups except predators. Resource consumption rates did not change seasonally, but total annual organic matter consumption rates varied greatly among the dominant invertebrate scraper (Farrodes, 0.85 g/m2 /yr), filterer (Macronema, 7.6 g/m2 /yr), collector-gatherer (Chironomidae, 2.7 g/m2 /yr), and predator (Tanypodinae, 1.0 g/m2 /yr). The dominant shredder, Anchytarsus, consumed ~0.40 g/m2 /yr of coarse organic matter. Organic matter consumption by dominant tadpole taxa was 0.27 g/m2 /yr. This is the first study to examine the TBP in a neotropical stream, and it will allow for quantitative assessments of how amphibian declines may affect energy flow.