the role of environmental and biological factors in determining Arctic species richness and community structure

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One of the most striking, but least understood, features of the biological world is its enormous diversity. Explaining the origin and maintenance of biodiversity is a long-standing puzzle in ecology and evolution. Competition might be intuitively expected to eliminate all but one or a few fit species in each major ecological category, but this is clearly not the case. My work focuses on characterizing and explaining patterns of species richness and co-existence in Arctic ecosystems. These systems are ideal targets for community-wide analyses due to their lower biodiversity compared with southern systems. Moreover, the proposed research is facilitated by the fact that numerous collaborators and I have been working for several years at a low-Arctic Canadian site (Churchill, Manitoba) to build a "DNA barcode reference library", which permits the identification of larval life stages and small cryptic organisms using DNA sequences. Such life stages commonly constitute the most abundant and diverse ecosystem elements, and problems with identification previously limited our ability to conduct community analyses. This recent work has enabled biodiversity and community structure analysis on a scale that would have been impossible only a few years ago. The proposed research will test whether Arctic communities simply consist of species that were able to colonize and survive in this environment or whether there is evidence of community structuring via biological interactions such as competition and predation. This work will be novel in scale, encompassing a broad range of invertebrate groups, terrestrial and freshwater habitats, local and regional geographic scales, and multiple trophic levels. This coverage will permit assessments of whether observed patterns are system specific or reflect more general ecological principles of community assembly. This work is expected to contribute to resolving the debate over the relative roles of different types of deterministic forces, including habitat selectivity and biotic interactions, as opposed to stochasticity in influencing community diversity and structure.