Environmental and ecological drivers of food web structure and dynamics

McLeod, Anne (2020) Environmental and ecological drivers of food web structure and dynamics. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Natural communities are undergoing accelerated changes due to human pressures such as habitat fragmentation, over-harvesting, and species invasions. Here, I use bioinformatics and mathematical models to examine the environmental and ecological drivers of food-web structure and dynamics. First, I use a spatially expansive food web to examine drivers of spatial turnover in food web interactions across an environmental gradient. I observe that there is a large amount of spatial turnover in food web interactions, however, the fundamental structure of these food webs stays constant. Further, I demonstrate that predicting local realizations of community structure is very difficult, but critical since environmental perturbations occur at the local scale. Then, I integrate empirical data and mathematical models to explore the consequences of omnivory on food-web stability and persistence. I demonstrate that the importance of omnivory depends on both the type of omnivory and the food web within which it appears. Moreover, scale matters - conclusions about the stabilizing effect of omnivory depend on the scale of the mathematical model (i.e. module vs whole food web model). Omnivory is just one repeated structure within food webs. Using a dynamic food web model, I examine the relationship between different network metrics and community, species, and interaction persistence in food webs. I demonstrate that network metrics are successful at predicting community and interaction persistence. They are not, however, the same metrics, and the relationship is dependent on the scale of persistence being examined (i.e community vs species vs interaction). Finally, I derive a novel multi-trophic metacommunity model which demonstrates how movement is a product of both a species’ ability to move and the landscape across which it moves. Treating patch connectivity as a species’ specific property can change our conclusions about multi-patch stability. Overall, my thesis integrates data and theory to test the impacts of environmental gradients and change on food webs and provide testable predictions to guide future research in spatial food web ecology.

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