Individual specialization and the trophic niche of aquatic consumers

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Animals obtain their energy and nutrients from eating other organisms, and in turn, may themselves become food for other consumers. The study of these feeding relationships is called trophic ecology, and the network of feeding relationships in an ecosystem is called a food web. A species' functional role in an ecosystem is called its niche, and is defined by the resources it uses, both habitat and food. The trophic niche is that part of the niche defining what the species eats. Positions and dimensions of trophic niches of species in an ecosystem, as well their abundances, define the ecosystem food web structure. This structure affects energy and material flows, and the quantity and quality of foods ultimately available to us. Research on the trophic niche helps us to understand food web structure, as well as ecological and evolutionary processes.******The trophic niche of a species can be thought of as a space defined by the types and relative abundances of foods eaten. Species that eat a diversity of food types are said to occupy a large trophic niche. Populations are composed of individuals that differ from each other in various ways, including their trophic ecologies. A fascinating finding of recent research is that many species exhibit strong individual trophic specialization. That is, even though the trophic niche of the population may be large, individuals each tend to focus their feeding on a smaller, particular subset of food types. This phenomenon is very interesting to evolutionary ecologists because it may reflect the early stages of differentiation that eventually leads to speciation. My research program examines the trophic ecology of aquatic organisms using individual specialization as an index of trophic niche size.******A variety of techniques are used to measure the trophic niche. My research program will primarily use ecological tracers, in particular stable isotopes. These are measures of the chemical composition of an organism that reflect long-term dietary patterns. I will use ecological tracer data along with recently developed data analyses methods to estimate the trophic niche sizes of fish populations, and examine how they vary with respect to environmental conditions in lakes and rivers of the boreal shield ecoregion. I will also conduct laboratory experiments to test key assumptions about how ecological tracer data can be used and interpreted.******This research will help us to understand how the environment influences the specialization and diversification processes in animal populations, and how this influences the numbers and types of species that can co-exist. It will also help us understand how freshwater food webs function and may be altered by human activities, and this will improve our management of these aquatic systems. Finally, my laboratory experiments will allow us to refine how we use ecological tracers, and will broaden their application in ecological and environmental research.