Data from: The effects of pastoral intensification on the feeding interactions of generalist predators in streams
Pearson, Caitlin E. et al. (2017), Data from: The effects of pastoral intensification on the feeding interactions of generalist predators in streams, Dryad, Dataset, https://doi.org/10.5061/dryad.0hb5n
Land use change can alter trophic interactions with wide-ranging functional consequences, yet the consequences for aquatic food webs have been little-studied. In part, this may reflect the challenges of resolving the diets of aquatic organisms using classical gut contents analysis, especially for soft-bodied prey. We used next generation sequencing to resolve prey use in nearly 400 individuals of two predatory invertebrates (the Caddisfly, Rhyacophila dorsalis, and the Stonefly Dinocras cephalotes) in streams draining land with increasingly intensive livestock farming. Rhyacophila dorsalis occurred in all streams, whereas D. cephalotes was restricted to low intensities, allowing us to test whether: i) apparent sensitivity to agriculture in the latter species reflects a more specialised diet and ii) diet in R. dorsalis varied between sites with and without D. cephalotes. DNA was extracted from dissected gut contents, amplified without blocking probes and sequenced using Ion Torrent technology. Both predators were generalists, consuming 30 prey taxa with preference for taxa that were abundant in all streams or that increased with intensification. Where both predators were present, their diets were nearly-identical, and R. dorsalis’s diet was virtually unchanged in the absence of D. cephalotes. The loss of D. cephalotes from more intensive sites was probably due to physicochemical stressors, such as sedimentation, rather than to dietary specialization, although wider biotic factors (e.g. competition with other predatory taxa) could not be excluded. This study provides a uniquely detailed description of predator diets along a land use intensity gradient, offering new insights into how anthropogenic stressors affect stream communities.
National Science Foundation, Award: No