Habitat-mediated cannibalism and microhabitat restriction in the stream invertebrate <Emphasis Type="Italic">Gammarus pulex</Emphasis> |
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Authors: | Kathleen E McGrath Edwin T H M Peeters John A J Beijer Marten Scheffer |
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Institution: | (1) Aquatic Ecology and Water Quality Management Group, Wageningen University, Postbus 8080, 6700 DD Wageningen, The Netherlands;(2) Present address: Biology Department, Washington State University, 2710 University Drive, Richland, WA 99354, USA |
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Abstract: | In cannibalistic species, small individuals often shift habitats to minimize risk of predation by larger conspecifics. The
availability of diverse size-structured habitats may mediate the incidence of cannibalism by larger individuals on smaller
individuals and increase fitness of smaller individuals. We tested these hypotheses in a series of laboratory studies with
Gammarus pulex, a freshwater amphipod inhabiting substrates with varying interstitial pore space sizes. In the absence of larger, potentially
cannibalistic individuals, small Gammarus actively used all pore space sizes offered. They used only substrates containing food and preferred food items that provided
cover to food items that did not. In the presence of larger G. pulex, small individuals almost exclusively used smaller pore spaces from which larger individuals were excluded. Small individual
survival was significantly lower in the presence of larger Gammarus than in controls without larger individuals regardless of substrate size, but availability of mixed pore sizes significantly
increased survival. Food consumption and growth per individual were not affected by the presence of larger individuals or
substrate composition. Our results suggest that the distribution and availability of complex and high-quality habitats may
affect the occurrence and significance of cannibalism in size-structured populations.
Handling editor: K. Martens |
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Keywords: | Substrate Body size Gammarus pulex Abiotic– biotic interactions Microhabitat |
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