The role of ecological interactions: how intrinsic and extrinsic factors shape the spatio-temporal dynamics of populations

摘要

How individuals respond to environmental demands and pressures from conspecifics and from other species determines whether they will survive and reproduce, and hence whether their populations will persist. However, not all environments are benign or predictable, and not all populations of the same species respond to environmental pressures in the same way. The overall objective of this thesis was to incorporate both biotic and abiotic interactions into one conceptual framework to better understand and predict how species’ populations change across space and time. To help progress this objective, I built a trophic interaction model to capture the complexity of biotic and abiotic interactions in a model arid system, using long-term (over 20 years) ecological data on small vertebrates, climate and vegetation replicated across a large spatial area (8000 km2). The model was built upon smaller components that investigated the spatial and temporal dynamics of species’ populations and their biotic and abiotic drivers. A key achievement of this thesis is that it clarifies and confirms the importance of both biotic and abiotic interactions in arid resource-pulse environments. The trophic interaction model advances our knowledge on how interactions are context-specific and can change over space and time. It incorporates both bottom-up and top-down processes, and shows how the relative strength of these processes can change. I show also that simultaneous analysis of abiotic factors is important in predicting changes in species’ populations, and that biotic interactions (e.g. predation) can limit increases in consumer populations. In order to make accurate predictions about how species and ecological processes will respond to environmental change in arid systems, both biotic and abiotic factors need to be incorporated explicitly into models.