UBC Theses and Dissertations

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UBC Theses and Dissertations

Scaling from species' traits to the maintenance of biodiversity in a changing world Forbes, Coreen


Patterns of biodiversity and the processes generating them vary over scales of time, space, and ecological organization. This scale dependency is one of the foremost obstacles to understanding how biodiversity responds to global change. The problem of scale has inspired and shaped many theoretical frameworks in ecology, but despite many attempts to unify ecological understanding across scales, this goal remains elusive. It is becoming increasingly clear that a more unified view of ecology will require us to draw from multiple ecological theories. Attributes of organisms that determine their fitness, known as “species’ traits”, are a common feature of many scaling theories and may help to unify our understanding of ecology across scales. In this thesis, I drew from The Metabolic Theory of Ecology, Modern Coexistence Theory, and Metacommunity Theory to understand how processes that determine patterns of abundance and diversity relate to measurable species’ traits. I combined theory with experiments in which I manipulated temperature, a key factor in climate change, and distance between habitat patches, a key element of land use change and fragmentation. I conducted laboratory experiments in a pond zooplankton system to test how species’ traits determining thermal performance relate to how populations and communities respond to temperature. Contrary to theoretical predictions, I showed that temperature sensitivities increase with scale from individual-level metabolism to resource consumption to population growth. My results also reveal that an essential element that determines how strongly species compete, stabilizing niche differences, change with temperature altering competitive outcomes, and the maintenance of biodiversity. This is the first test of the temperature dependence of niche differences. Lastly, I conducted field experiments in an eelgrass community to test whether the movement of invertebrates at the regional scale affected their diversity at the local scale. I showed that invertebrate species richness decreases with increasing eelgrass patch isolation, but this was not explained by species’ traits. My thesis has revealed scale dependence in key processes that maintain biodiversity. These results can help us better predict how biodiversity will change under climate change and habitat loss.

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