Habitat complexity does not influence prey consumption in an experimental three-level trophic chain
ABSTRACT Habitat complexity influences species diversity and regulates trophic interactions, mostly by increasing resource partitioning within habitats and providing refuge for prey. The influence of habitat complexity on more than two trophic levels is not well understood, mainly because behavioral modifications of prey and predator may influence the outcome of trophic interactions. Thus, we conducted a two-factor experiment with a three-level trophic chain: a piscivorous fish [Hoplerythrinus unitaeniatus (Spix & Agassiz 1829)], an invertivorous fish (Moenkhausia forestii Benine, Mariguela & C. de Oliveira, 2009) and an aquatic macroinvertebrate (Chironomidae larvae). We measured prey consumption in low, intermediate and high habitat complexity, provided by submerged macrophyte densities, in the presence and the absence of the piscivore, intending to test the hypothesis that higher habitat complexities decrease predators foraging success in different trophic levels. We calculated the percentage of consumed prey in all treatment combinations. There was no significant effect of habitat complexity on prey consumption for neither the piscivorous nor the invertivorous fish, but a positive correlation was found between the percentages of consumed prey by both the piscivore and the invertivore. Observed modifications in the foraging behavior of the piscivore may have resulted in similar prey consumptions in low and high macrophyte densities. Moreover, more active M. forestii could have suffered a higher predation pressure by H. unitaeniatus, resulting in the positive correlation found. We conclude that behavior patterns in different habitat complexities possibly influenced predation rates in the three experimental trophic levels.