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Habitat structure and prey aggregation determine the functional response in a soil predator-prey interaction |
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| Authors: | Olivera Vucic-Pestic Björn C Rall Ulrich Brose |
| Institution: | a Darmstadt University of Technology, Institute of Zoology, Schnittspahnstr. 10, 64287 Darmstadt, Germany b Justus Liebig University Giessen, Institute of Animal Ecology, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany c Georg-August-University Göttingen, J.F. Blumenbach Institute of Zoology and Anthropology, Berliner Str. 28, 37073 Göttingen, Germany |
| Abstract: | Functional responses describe the per capita consumption rates of predators depending on prey density, which quantifies the energy transfer between trophic levels. We studied a typical interaction of the litter-soil systems between hunting spiders (Pardosa lugubris; Araneae: Lycosidae) and springtails (Heteromurus nitidus; Collembola: Entomobryidae) at varying habitat structure, i.e. with moss vs. without moss. We found a hyperbolic increase in consumption (functional response type II) in the treatment without habitat structure that was converted into a roller-coaster (or dome-shaped in a broad sense) functional response in treatments with habitat structure. Additional experiments suggest that the reduced per capita consumption rates at high prey densities may be explained by aggregative defence behaviour of the springtails. Experimentally, this behaviour was induced by the presence of habitat structure. We analyzed the net-energy gain of this predator-prey interaction by comparing the predator’s metabolic energy loss to its energy gain by consumption. In treatments with habitat structure, the net-energy gain of the predator was limited at intermediate prey densities where prey aggregation reduced the consumption rates. Our results stress the importance of habitat structure and prey behaviour in shaping the functional response in a typical soil-litter predator-prey interaction. |
| Keywords: | Type IV functional response Dome-shaped functional response Metabolic rate Swarming effect Interaction strength |
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