title: Antagonistic effects of biological invasion and environmental warming on detritus processing in freshwater ecosystems.
abstract: Global biodiversity is threatened by multiple anthropogenic stressors but little is known about the combined effects of environmental warming and invasive species on ecosystem functioning. We quantified thermal preferences and then compared leaf-litter processing rates at eight different temperatures (5.0-22.5 °C) by the invasive freshwater crustacean Dikerogammarus villosus and the Great Britain native Gammarus pulex at a range of body sizes. D. villosus preferred warmer temperatures but there was considerable overlap in the range of temperatures that the two species occupied during preference trials. When matched for size, G. pulex had a greater leaf shredding efficiency than D. villosus, suggesting that invasion and subsequent displacement of the native amphipod will result in reduced ecosystem functioning. However, D. villosus is an inherently larger species and interspecific variation in shredding was reduced when animals of a representative size range were compared. D. villosus shredding rates increased at a faster rate than G. pulex with increasing temperature suggesting that climate change may offset some of the reduction in function. D. villosus, but not G. pulex, showed evidence of an ability to select those temperatures at which its shredding rate was maximised, and the activation energy for shredding in D. villosus was more similar to predictions from metabolic theory. While per capita and mass-corrected shredding rates were lower in the invasive D. villosus than the native G. pulex, our study provides novel insights in to how the interactive effects of metabolic function, body size, behavioural thermoregulation, and density produce antagonistic effects between anthropogenic stressors.
authors.affiliation: School of Biology and water@leeds, University of Leeds, Leeds, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kenna
authors.affiliation: School of Biology and water@leeds, University of Leeds, Leeds, UK.
authors.forename: William N W
authors.initials: WN
authors.lastname: Fincham
authors.affiliation: School of Biology and water@leeds, University of Leeds, Leeds, UK.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Dunn
authors.affiliation: School of Geography and water@leeds, University of Leeds, Leeds, UK.
authors.forename: Lee E
authors.initials: LE
authors.lastname: Brown
authors.affiliation: School of Biology and water@leeds, University of Leeds, Leeds, UK. c.hassall@leeds.ac.uk.
authors.forename: Christopher
authors.identifier: 0000-0002-3510-0728
authors.initials: C
authors.lastname: Hassall
mesh_terms: D000818:Animals; D057231:Climate Change; D017753:Ecosystem; D005618:Fresh Water; D058865:Introduced Species; D006113:United Kingdom
keywords: Amphipod; Climate change; Leaf-litter; Resource processing; Temperature