, Volume 163, Issue 3, pp 625–636 | Cite as

Spatial heterogeneity and functional response: an experiment in microcosms with varying obstacle densities

  • Céline HauzyEmail author
  • Thomas Tully
  • Thierry Spataro
  • Grégory Paul
  • Roger Arditi
Population ecology - Original Paper


Spatial heterogeneity of the environment has long been recognized as a major factor in ecological dynamics. Its role in predator–prey systems has been of particular interest, where it can affect interactions in two qualitatively different ways: by providing (1) refuges for the prey or (2) obstacles that interfere with the movements of both prey and predators. There have been relatively fewer studies of obstacles than refuges, especially studies on their effect on functional responses. By analogy with reaction–diffusion models for chemical systems in heterogeneous environments, we predict that obstacles are likely to reduce the encounter rate between individuals, leading to a lower attack rate (predator–prey encounters) and a lower interference rate (predator–predator encounters). Here, we test these predictions under controlled conditions using collembolans (springtails) as prey and mites as predators in microcosms. The effect of obstacle density on the functional response was investigated at the scales of individual behavior and of the population. As expected, we found that increasing obstacle density reduces the attack rate and predator interference. Our results show that obstacles, like refuges, can reduce the predation rate because obstacles decrease the attack rate. However, while refuges can increase predator dependence, we suggest that obstacles can decrease it by reducing the rate of encounters between predators. Because of their opposite effect on predator dependence, obstacles and refuges could modify in different ways the stability of predator–prey communities.


Encounter rates Habitat complexity Mutual interference Predator–prey interaction 



We thank A.-S. Barbero, K. Jaouannet and Q. Renault for their technical assistance. We are grateful to CEREEP for providing an excellent working environment at the field station where this work was carried out. We thank M. van Baalen for stimulating discussions and Monika Ghosh for assistance with the English. C.H. thanks R.A. for funding this research during a short postdoc at AgroParisTech. This research complies with all applicable regulatory requirements.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Céline Hauzy
    • 1
    • 3
    • 4
    Email author
  • Thomas Tully
    • 1
    • 2
  • Thierry Spataro
    • 1
    • 3
  • Grégory Paul
    • 5
  • Roger Arditi
    • 1
    • 3
  1. 1.UMR7625 Écologie et ÉvolutionUniversité Pierre et Marie CurieParisFrance
  2. 2.IUFM de ParisUniversité Paris 4 - SorbonneParisFrance
  3. 3.USC2031-INRA Écologie des populations et communautésAgroParisTechParisFrance
  4. 4.IFM Theory and ModellingLinköping UniversityLinköpingSweden
  5. 5.Institute of Theoretical Computer Science and Swiss Institute of BioinformaticsETH ZürichZurichSwitzerland

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