Inducible defences in food webs

Vos, M., Kooi, B.W., DeAngelis, D.L. and Mooij, W.M. 2006. Inducible defences in food webs. In: P. C. de Ruiter, V. Wolters and J. C. Moore (eds) Dynamic Food Webs: Multispecies assemblages, ecosystem development, and environmental change {A} volume of Theoretical Biology: 114-127


Inducible defenses cause heterogeneities within prey populations that have major effects on food web dynamics. Recent theoretical work demonstrates that inducible defenses can stabilize trophic interactions, offering one possible resolution to the paradox of enrichment. This work also predicts that inducible defenses lead to all trophic levels gradually increasing under enrichment. Such a pattern in trophic level responses has been observed in both aquatic and terrestrial systems in nature.

Inducible defenses are often consumer-density dependent. Thus they structure per capita interaction strengths in multitrophic communities. This is one of the reasons why values for interaction strengths deviate from random in natural food webs.

The fractions of defended and undefended individuals within prey populations may shift back and forth in response to fluctuating consumer densities. Such a dynamic heterogeneity within prey food web nodes causes a type of food web flexibility that has received little attention in food web theory. Approaches that ignore the dynamics of heterogeneity within food web nodes may miss some of the mechanisms that actually underlie the observed patterns and processes in real food webs.

Here we present a short overview of inducible defense effects on community level properties such as local stability and persistence, and show novel results on the resilience of systems where defenses are inducible, permanent or absent.

The study of inducible defense effects on these community level properties is a relatively novel field. As a consequence this overview contains a relatively high proportion of references to our own work.

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