Dissertation Research: The Effects of Phenotypic Variation on Food Web Architecture and Ecosystem Fluxes: A Dual Tracer Isotope Approach

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The primary goal of this study is to determine how variation within a single species can influence the transfer of energy and materials in stream food webs. The proposed research will use a model system for evolutionary studies, the Trinidadian guppy (Poecilia reticulata), to determine how two phenotypes of a single species can influence ecosystem processes in streams. Streams on the island of Trinidad occur in parallel watersheds that have similar environmental gradients with locally adapted populations of guppies. Two phenotypes have been established in previous studies: guppies from streams with predators, and guppies from streams without predators. These two guppy phenotypes are likely to influence the ecosystem in unique ways because of differences in how they feed and what they eat. This study uses a replicated experiment to examine how both guppy phenotype and resource availability influence ecosystems.A better understanding of how within-species variation affects ecological processes will provide additional insight into interactions between ecological and evolutionary processes, which may be widespread and significant. Many people are familiar with guppies because of their prominent role in the aquarium trade, making them an accessible system to communicate scientific research about evolutionary ecology. This work will also inform studies of how land use change alters stream ecosystems.