Dodd J.A., Dick J.T.A., Alexander M.E., Macneil C., Dunn A.M., Aldridge D.C.
Predicting the ecological impacts of a new freshwater invader: Functional responses and prey selectivity of the 'killer shrimp', Dikerogammarus villosus, compared to the native Gammarus pulex
Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, United Kingdom; Aquatic Ecology Group, Department of Zoology, University of Cambridge, Cambridge, United Kingdom; Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa; Department of the Environment, Food and Agriculture, Isle of Man Government, Thie Slieau Whallain, St. Johns, Isle of Man, United Kingdom; School of Biology, University of Leeds, Leeds, United Kingdom
Dodd, J.A., Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, United Kingdom, Aquatic Ecology Group, Department of Zoology, University of Cambridge, Cambridge, United Kingdom; Dick, J.T.A., Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, United Kingdom; Alexander, M.E., Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa; Macneil, C., Department of the Environment, Food and Agriculture, Isle of Man Government, Thie Slieau Whallain, St. Johns, Isle of Man, United Kingdom; Dunn, A.M., School of Biology, University of Leeds, Leeds, United Kingdom; Aldridge, D.C., Aquatic Ecology Group, Department of Zoology, University of Cambridge, Cambridge, United Kingdom
The ability to predict the likely ecological impacts of invasive species in fresh waters is a pressing research requirement. Whilst comparisons of species traits and considerations of invasion history have some efficacy in this respect, we require robust methods that can compare the effects of native and invasive species. Here, we utilise comparative functional responses and prey selectivity experiments to understand and predict the ecological impact of an invader as compared to a native. We compared the predatory functional responses of an emerging invasive species in Europe, the 'killer shrimp', Dikerogammarus villosus, and an analogous native species, Gammarus pulex, towards three representative prey species: Asellus aquaticus, Daphnia magna and Chironomus sp. Furthermore, as ecological impact may be greater for invasive species with more indiscriminate feeding habits, we compared the selectivity for the three prey types between the invasive and native species. In both the presence and absence of experimental habitats, large D. villosus, and those matched for body size with G. pulex, generally showed higher (Type II) functional responses than G. pulex, with the invasive species exhibiting higher maximum feeding rates. Further, D. villosus exhibited significantly more indiscriminate prey selection compared with G. pulex, a trait that became more evident as the invader increased in size. Differences in functional responses and prey selectivity were prey species specific, with higher to lower predicted impacts in the order A. aquaticus, D. magna and Chironomus sp. This is in accord with the impact of this invasive species on macroinvertebrates in the field. We thus provide understanding of the known ecological impact of D. villosus and discuss the utility of the phenomenological use of comparative functional responses and resource use as a tool through which the potential ecological impacts of invasive species may be identified. © 2013 John Wiley & Sons Ltd.