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Contributed Talk

Session: : Food Webs 1

COS 14-6 - Drivers of food web patterns across North America

Monday, August 7, 2023
2:45 PM – 3:00 PM PDT
Location: D138
Abstract: Food webs are powerful tools for the visualization and structural assessment of biodiversity data, but their application has traditionally been limited to local systems due to the immense amount of ecological data and human effort required to construct them. Despite extensive theory about food web ecology, only a few examples of well-characterized food webs are documented in the literature, limiting application of food web analysis at larger spatial scales. Here, we capitalize on a large, multi-trophic dataset from the U.S. National Ecological Observatory Network (NEON) to generate trait-based food web models using a previously published pipeline. We constructed heuristic food webs for 24 wadeable NEON streams, across several seasons and years, and extracted their network properties to explore how they vary through space and time and what environmental drivers influence this variation. We then mined existing hydrological, chemical, and geomorphic information from the NEON data portal to assess what factors control the structure of these food webs, and what variables are associated with structural change through time. Coupling information extracted from our food web models with environmental data from the NEON portal, we then tested the following hypotheses. H1: Overall, stream temperature will be the key driver of food web structural metrics because these streams will support more productivity and diversity of taxa. Specifically, we predict that as stream temperature increases, food webs will become larger, more complex, and have higher maximum trophic levels. H2: Hydrologically variable systems will be less controlled by stream temperature and will have more variable food web metrics because hydrological flushing will frequently reset these systems. H3: Food web stability across seasons and years will be higher in streams that have a higher diversity of aquatic organisms because of higher functional redundancy of feeding guilds in these rivers. Preliminary findings indicate that higher elevation streams had larger metawebs with higher connectance, but these food webs were also more variable through time. Additionally, within the continental US, there was also a latitudinal gradient, with larger metawebs occurring at higher latitudes; this pattern, however, did not hold with Alaska streams, which had much smaller metawebs. The most stable food webs tended to occur in the middle part of the continental United States. Results from our study provide important insights into what large-scale drivers affect the structure of aquatic food webs and what confers their stability over space and time.