Trophic ecology of alpine stream invertebrates: current status and future research needs

Community structures of benthic invertebrates in different alpine stream types have been well documented and modeled against environmental conditions and change. However, community structure cannot be linked directly to community functions or processes, and this problem prevents clear estimation of functional consequences of environmental changes. In this article, we highlight the need to focus research efforts on the trophic ecology of alpine streams for several reasons. 1) The trophic ecology of invertebrates is remarkably understudied in the field of alpine stream ecology (only 7% of published studies), but the trophic ecology of invertebrates underlies crucial functions in these ecosystems. 2) Classifications of species into functional feeding groups, traits often used to express the functionality of invertebrate communities, are missing for several alpine species or have been deduced from classifications based on higher taxonomic levels. 3) Most investigators focused on a few trophic levels, whereas use of new analytical methods, such as Bayesian stable-isotope mixing models could provide statistically sophisticated estimations of multiple food-source contributions to consumers' diets. 4) Out-dated ideas need to be revised; e.g., we demonstrate that Diamesa species can actively select their food, which is against the established assumption that animals in harsh environments are forced to feed on everything they can get. Based on literature studies, we summarized most critical research needs on the trophic ecology of alpine stream invertebrates. Our goal is to promote ways to understand the ecological function of alpine stream invertebrates and the potential effects of alteration of their trophic relationships by ongoing environmental changes like glacier retreat, water exploitation, or immigration of invasive species.