Comparison of the dietary composion of epilithic trichopteran species in a first-order stream

The dietary composition of six epilithic trichopteran species, each with a similar life cycle, was examined. In 1896 and 1987 the gut contents of later stage larvae were analyzed and comparisons were made between specimens sampled along the lower 2 km of a Central European first-order stream. Gut contents were classified into 9 components and quantified using image analysis. Statistical analysis revealed significant differences between the utilization of several food components by the six species considered, despite an overlap in their microhabitats and food resources. The gut contents of Drusus annulatus, Tinodes rostocki, Micrasema longulum contained a high proportion of diatoms, whereas cyanobacteria were abundant in Apatania fimbriata and D. annulatus. There were fewer algae, but higher proportions of detritus, in Agapetus fuscipes and Silo pallipes. Seasonal variability in periphyton composition was partly reflected in the larval gut contents. A cluster analysis revealed three species groupings: A. fuscipes and S. pallipes showed the most distinct trophic niche overlap, followed by A. fimbriata and D. annulatus. T. rostocki and M. longulum were combined in one group at a lower similarity level. Significant differences between the utilization of several food components reduced the likelihood of any inter-specific competition for high quality food resources. (Author's abstract