UBC Theses and Dissertations
Exploring the relationship between functional diversity and resilience in coral reef communities with an agent-based model Carturan, Bruno S.
Corals are foundation species whose diversity regulates the functioning of coral reef ecosystems. Climate change and anthropogenic disturbances change the species composition of coral communities, and jeopardize reef persistence. Our capacity to mitigate these impacts is limited by key knowledge gaps about how coral diversity and specifically coral functional traits influence the resilience of reef ecosystems. In other ecosystems, experiments have shown support for the diversity-resilience hypothesis, whereby greater functional diversity enhances ecosystem resilience. Analogous evidence in reef ecosystems is lacking, in part because the high diversity and structural complexity of coral reefs render manipulative experiments infeasible at relevant temporal and spatial scales. Simulation models can overcome these limitations, but to date such models have been limited in their inclusion of relevant trait data and representation of key ecological processes. My goal was to test the diversity-resilience hypothesis for reef ecosystems, focusing primarily on coral species. Building on previous efforts by plants ecologists, we first developed the effect, resistance and recovery trait framework, which accounts for processes of resistance and recovery—the two components of resilience. We illustrated via simulations how the framework can be used to predict the resilience of ecosystem functions. Using the framework, we then developed an agent-based model combining trait-based and demographic approaches to simulate community dynamics from the scale of coral polyps to the entire community. Built from empirical data and expert knowledge, the model simulates processes with an unprecedented degree of detail, and can be configured to represent diverse coral communities. After calibration, the model captured the dynamics of three Caribbean coral communities that were affected by cyclones and bleaching, and produced realistic patterns of cover, recruitment and colony size distributions. Lastly, we used the model to conduct a virtual experiment in which the initial functional trait diversity of coral communities was manipulated. These communities were subjected to cyclone and bleaching disturbances, and resilience was estimated by measuring their resistance, recovery rate and cover and rugosity 10 years after the disturbances. Using generalized linear models and model averaging, we found strong support for the diversity-resilience hypothesis: functional richness contributes significantly and positively to resilience.
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