Perturbations to the density of a species can be propagated to distant members of a food web via shifts in the density or the traits (i.e. behavior) of intermediary species. Predators with differing foraging modes may have different effects on prey behavior, and these effects may be transmitted differently through food webs. Here we test the hypothesis that shifts in the type of predator present in a food web indirectly affect the prey's resource independent of changes in the density of prey. We assessed the importance of predator identity in mediating the grazing effects of the freshwater snail Physa integra on its periphyton resources using field and mesocosm studies. Field observations showed that Physa used covered habitats more in ponds containing fish than in ponds containing crayfish or no predators at all. A field experiment confirmed that snail behavior depended on predator identity. Physa placed near caged pumpkinseed sunfish (Lepomis gibbosus) selected covered habitats, but Physa placed near caged crayfish (Orconectes rusticus) moved to the surface of the water. The effects of predator identity on periphtyon were then examined in a mesocosm experiment, using caged predators. Habitat use of Physa was similar to their habitat use in the field experiment. In the presence of caged sunfish, periphyton standing crop in covered habitats was reduced to 34% of the standing crop in the presence of crayfish. In contrast, periphyton in near-surface habitats was 110% higher in the presence of fish than in the presence of crayfish. Thus, the effects of predator identity on Physa behavior cascaded through the food web to affect the abundance and spatial distribution of periphyton.
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Univ Tokyo, Dept Gen Syst Studies, Meguro Ku, Tokyo 1538902, Japan
Univ Eastern Finland, Dept Biol, Joensuu, Finland
Kyoto Univ, Ctr Ecol Res, Otsu, Shiga, JapanUniv Tokyo, Dept Gen Syst Studies, Meguro Ku, Tokyo 1538902, Japan
Utsumi, Shunsuke
Kishida, Osamu
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Hokkaido Univ, Field Sci Ctr No Biosphere, Horonobe, JapanUniv Tokyo, Dept Gen Syst Studies, Meguro Ku, Tokyo 1538902, Japan
Kishida, Osamu
Ohgushi, Takayuki
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Kyoto Univ, Ctr Ecol Res, Otsu, Shiga, JapanUniv Tokyo, Dept Gen Syst Studies, Meguro Ku, Tokyo 1538902, Japan
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Univ Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Univ Calif Davis, Environm Sci & Policy, Davis, CA 95616 USAUniv Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Morgan, Steven G.
Gravem, Sarah A.
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Univ Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Oregon State Univ, Dept Integrat Biol, Corvallis, OR 97331 USAUniv Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Gravem, Sarah A.
Lipus, Adam C.
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Univ Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USAUniv Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Lipus, Adam C.
Grabiel, Marcos
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Univ Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USAUniv Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
Grabiel, Marcos
Miner, Benjamin G.
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Western Washington Univ, Dept Biol, Bellingham, WA 98225 USAUniv Calif Davis, Bodega Marine Lab, Bodega Bay, CA 94923 USA
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Department of Biological Sciences, Louisiana State University, Baton Rouge, 70803, LADepartment of Biological Sciences, Louisiana State University, Baton Rouge, 70803, LA
Cronin J.T.
Goddard J.
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Department of Mathematics, Auburn University Montgomery, Montgomery, 36124, ALDepartment of Biological Sciences, Louisiana State University, Baton Rouge, 70803, LA
Goddard J.
Muthunayake A.
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Department of Mathematics and Statistics, University of North Carolina at Greensboro, Greensboro, 27412, NCDepartment of Biological Sciences, Louisiana State University, Baton Rouge, 70803, LA
Muthunayake A.
Shivaji R.
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Department of Mathematics and Statistics, University of North Carolina at Greensboro, Greensboro, 27412, NCDepartment of Biological Sciences, Louisiana State University, Baton Rouge, 70803, LA