Natural born killers: an invasive amphipod is predatory throughout its life-history
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Introduced predators can have profound impacts on prey populations, with subsequent ramifications throughout entire ecosystems. However, studies of predator–prey interaction strengths in community and food-web analyses focus on adults or use average body sizes. This ignores ontogenetic changes, or lack thereof, in predatory capabilities over the life-histories of predators. Additionally, large individual predators might not be physically capable of consuming very small prey individuals. Both situations are important to resolve, as native prey may or may not therefore experience ontogenetic or size refuges from invasive predators. Here, we find that the freshwater amphipod invader, Gammarus pulex, is predatory throughout its development from juvenile through to adult. All size classes collected in the field had a common prey, nymphs of the mayfly Baetis rhodani, in their guts. In an experiment with predator, prey and experimental arenas scaled for body size, G. pulex juveniles and adults consumed B. rhodani in all size-matched categories. In a second experiment, the largest G. pulex individuals were able to prey on the smallest B. rhodani. Thus, the prey do not benefit from any ontogenetic or size refuge from the predator. This corroborates with the known negative population abundance relationships between this invasive predator and its native prey species. Understanding and predicting invasive predator impacts will be best served when interactions among all life-history stages of predator and prey are considered.
KeywordsAmphipod Community impacts Invasive species Ontogeny Predation
We thank the Natural Environment Research Council for funding, Chris Harrod for advice and the two referees for constructive comments.
- Dick JTA (2008) Role of behaviour in biological invasions and species distributions; lessons from interactions between the invasive Gammarus pulex and the native G. duebeni (Crustacea: Amphipoda). Contrib Zool 77:91–98Google Scholar
- Juliano SA (2001) Non-linear curve fitting: predation and functional response curves. In: Scheiner SM, Gurevitch J (eds) Design and analysis of ecological experiments. Oxford University Press, Oxford, pp 178–196Google Scholar
- Lipcius RN, Hines AH (1986) Variable functional responses of a marine predator in dissimilar homogenous microhabitats. Ecology 67:1361–1371Google Scholar
- Woodward G, Warren P (2007) Body size and predatory interactions in freshwaters: scaling from individuals to communities. In: Hildrew AG, Raffaelli DG, Edmonds-Brown R (eds) Body size: the structure and function of aquatic ecosystems. Cambridge University Press, Cambridge, pp 98–117CrossRefGoogle Scholar