DOI: 10.5061/dryad.78g8h50
title: Data from: Species turnover and invasion of dominant freshwater invertebrates alter biodiversity-ecosystem function relationship

description: Freshwater ecosystems rely on allochthonous resources. Integration of
 these subsidies depends on diversity of both terrestrial resources and
 aquatic shredder and decomposer communities, but the diversity effects on
 leaf litter breakdown and decomposition are less clear in aquatic than
 terrestrial ecosystems. We need a better understanding of this
 relationship because aquatic communities are rapidly changing with species
 invasions and anthropogenic impacts. Here, we experimentally disentangled
 the effects of leaf and shredder richness on leaf litter breakdown by
 macroinvertebrates in mesocosm experiments using three species of
 amphipods, a dominant guild of crustaceans in European freshwater
 ecosystems. Increased leaf richness led to lower-than-predicted leaf
 consumption by native shredders, with mixed evidence of resource-switching
 or prioritization of preferred food items within a leaf mix. Higher
 shredder species richness never promoted leaf consumption rates compared
 to predictions from relevant single-species experiments, and instead
 sometimes substantially decreased leaf consumption. We then conducted a
 meta-analysis of leaf litter consumption rates by seven widely distributed
 amphipod species (the three used in the experiments and four additional
 species). As expected based on our own experiments, non-native amphipod
 species generally had lower biomass-adjusted leaf litter consumption
 rates, although their larger body size led to higher per-individual leaf
 consumption rates. Contamination of the water by metals, pesticides and
 other chemicals additionally significantly decreased leaf litter
 consumption by multiple native and non-native species compared to
 unpolluted systems. While the meta-analysis suggested that litter
 consumption, and thus breakdown, would decline if native shredders are
 replaced by non-native heterospecifics, complete species replacement is
 not the only outcome following immigration in a meta-community context.
 Our experiments suggest that breakdown rates could remain reasonably high
 where native species coexist with non-native arrivals. Experiments which
 neglect the ecological realism of species coexistence will necessarily
 mischaracterize effects on ecosystem functioning.
description: Experiment_I_dataLeaf litter consumption data from an experiment manipulating leaf litter richness (one to six species of leaf litter) offered to Gammarus fossarum amphipods in experimental mesocosms.Experiment_II_dataLeaf litter consumption in an experiment manipulating amphipod species richness (1-3 amphipod species) in experimental mesocosms.allometric_dataSize-to-weight allometrics for six species of leaf litter used in Experiment I and II.C-N_litterCarbon and nitrogen content of six species of leaf litter used in Experiment I and II.P_litterPhosphorus content of six species of leaf litter used in Experiment I and II.Meta-analysis_dataData on leaf litter consumption by amphipods used in the meta-analysis, including conversion factors used to standardize units across studies.