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Title: Trophic interaction modifications in food webs
Author: Terry, James C. D.
ISNI:       0000 0004 7652 9146
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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Trophic interaction modifications are an important, but historically neglected, set of relationships between species within ecological communities. They define how the rate of consumption of a resource by a consumer is affected by the population of other species in the ecosystem. These modifications can derive from a wide range of ecological processes, and individual modifications have been shown to have major effects in small systems. Here I develop ecological understanding of interaction modifications at the whole network scale using theoretical analyses of generalised models. First, I examine in detail how interaction modifications can be considered as distinct processes to conventional pairwise interactions, demonstrating that otherwise disparate ecological processes can be united through a common framework that allows systematic and precise analysis. I illustrate this with a discussion of how the strength of an interaction modification can be understood from multiple angles and contexts. Second, I use models of artificial ecological communities to test for the properties that determine the importance of particular interaction modifications for the dynamics of whole communities in terms of directional predictability of responses to perturbations and local stability. I find that, in general, interaction strength-based methods are more effective than topological based metrics of key modifications. Third, I examine the impact that structured distributions of interaction modifications within ecological communities can have on the overall pattern of dynamic interactions and the resultant consequences for the stability of ecosystems. I demonstrate that certain reasonable distributions of interaction modifications can generate significant additional structure. Fourth, I directly test the impact of the multi-species nature of interaction modifications on the robustness of ecological communities to extinctions in response to sustained perturbations using generalised models of ecosystems. I show that interaction modifications shift the relative vulnerability of species and that higher-order models give notable different results to pairwise representations. I conclude with a discussion of approaches to gather network-level empirical data of the distribution of interaction modifications in order to translate the theoretical advances into natural systems.
Supervisor: Morris, Rebecca ; Bonsall, Michael Sponsor: Natural Environmental Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Zoology ; Ecology ; Networks