Temporal dynamics of interaction strength in quantitative food webs: an integration of spatial food web theory with empirical patterns of host-parasitoid interactions

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Food webs are crucial drivers of ecosystem processes and biodiversity. Variation in resource densities may be a key determinant of network dynamics. Single consumer-resource dynamics can be described in the framework of optimal foraging theory, but consumer responses to resource densities in multi-species cases and on landscape scales are only beginning to be formally described. Recent food web theory has highlighted the importance of switching behavior and coupling among habitats. In this project, we will use a longterm dataset of parasitoid-host food webs collected in boreal forest plots to understand quantitative food web dynamics. In this system, the caterpillar, spruce budworm, is a major herbivore pest that may drive food web structure. We will test if empirical patterns match landscape-level food web theory. Our core objectives are (i) to empirically determine temporal dynamics of interaction strengths in relation to density of an outbreak species in a complex food web, (ii) to determine how this food web-level response changes between low and high diversity landscapes and identify which processes contribute to this response, and (iii) to develop a model to formally describe how a focal species is affected by food web structure. Finally, this model will be generalized to different network types. Our project will illustrate how temporal food web dynamics are influenced by community composition and foraging behavior. It will generate specific hypotheses to guide future research and provide a basis for improving pest management practices.