Predator identity and the nature and strength of food web interactions

Authors

  • Lee M. Henry,

    Corresponding author
    1. Department of Zoology, University of Oxford, the Tinbergen Building, South Parks Road, Oxford OX1 3PS, UK
    2. Department of Biological Sciences, Simon Fraser University, Burnaby BC V5A 1S6, Canada
      Correspondence author. E-mail: lee.henry@zoo.ox.ac.uk
    Search for more papers by this author
  • Jordan A. Bannerman,

    1. Department of Biological Sciences, Simon Fraser University, Burnaby BC V5A 1S6, Canada
    Search for more papers by this author
  • David R. Gillespie,

    1. Department of Biological Sciences, Simon Fraser University, Burnaby BC V5A 1S6, Canada
    2. Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, POB 1000 Agassiz BC V0M 1A0, Canada
    Search for more papers by this author
  • Bernard D. Roitberg

    1. Department of Biological Sciences, Simon Fraser University, Burnaby BC V5A 1S6, Canada
    Search for more papers by this author

Correspondence author. E-mail: lee.henry@zoo.ox.ac.uk

Summary

1. Most trophic interaction theory assumes that all predators are an abstract form of risk to which prey respond in a quantitatively similar manner. This conceptualization can be problematic because recent empirical work demonstrates that variation in the responses of prey to different predators can play a key role in structuring communities and regulating ecosystem function.

2. Predator identity – the species specific response of prey to a predator – has been proposed as an ultimate mechanism driving the relative contribution of indirect effects in food webs; however few studies have explicitly tested this hypothesis.

3. This study explores the impact of predator identity on direct consumptive (CE) and non-consumptive effects (NCEs), and on the relative contribution of indirect, density and trait-mediated effects in trophic cascades within host-parasitoid communities.

4. We systematically compared the individual, host-parasitoid-plant interactions of two actively foraging parasitoid species with disparate foraging styles, one aggressive and one furtive, a common aphid host and plant. Our results demonstrate that the degree of risk aversion by prey to each particular predator species (i.e. predator identity) is a key factor driving the nature and strength of direct and indirect transmission pathways.

5. Both parasitoid species, in general, had a negative impact on plants. The magnitude of the aphid anti-predator dispersal response was positively correlated with plant infestation and plant damage. The qualitative effect of predator-induced infestation of new plants superseded the quantitative effects of predator-mediated reductions in aphid numbers.

6. The greatest indirect impact on plants was generated by the aggressively foraging parasitoid, and the strength of the aphids anti-predator response (a NCE) antagonistically traded-off with CEs due to an increased investment in attempting to capture risk-sensitized prey. In contrast, the furtive parasitoid did not elicit a strong anti-predator response, had little indirect impact on plants, but generated very high CEs due to the advantage of ovipositing into a sedentary prey population.

7. Our data suggest the responses of prey to different predatory cues may be an important mechanism driving the relative contribution of transmission pathways in trophic cascades. We conclude that predator identity is a key factor influencing the nature and strength of food web interactions.

Ancillary