DETERMINATION OF DIETS OF ALPINE AQUATIC INSECTS USING STABLE ISOTOPES AND GUT ANALYSIS

We used both traditional gut analyses and stable isotopes to determine the diets of macroinvertebrates from an alpine wetland at 3593 m (Colorado Front Range). The two methods agreed. The Trichopteran, Asynarchus curtus (Banks) consumed mostly detritus, while chironomid larvae consumed periphyton and/or detritus. Filamentous algae, however, were not consumed by any taxa studied. The value of combining both methods is illustrated for Orthocladius, which is shown to be more a generalist in its diet based on stable isotopes than a specialist based upon analysis of gut contents. The results suggest that the way an animal captures its food (functional feeding group) does not necessarily imply an obligate trophic status for it.