Habitat structure and prey aggregation determine the functional response in a soil predator-prey interaction

• Functionalresponses 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 habitatstructure, i.e. with moss vs. without moss. We found a hyperbolic increase in consumption (functionalresponse type II) in the treatment without habitatstructure that was converted into a roller-coaster (or dome-shaped in a broad sense) functionalresponse in treatments with habitatstructure. 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 habitatstructure. We analyzed the net-energy gain of this predator–preyinteraction by comparing the predator’s metabolic energy loss to its energy gain by consumption. In treatments with habitatstructure, the net-energy gain of the predator was limited at intermediate prey densities where preyaggregation reduced the consumption rates. Our results stress the importance of habitatstructure and prey behaviour in shaping the functionalresponse in a typical soil–litter predator–preyinteraction.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Type IV functional response

Dome-shaped functional response

Metabolic rate

Swarming effect

Interaction strength

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