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1. Incorporating positive interactions and mutualisms into ecological theory. Over twenty-five years ago, Sir Robert May bemoaned the dearth of attention paid to positive interactions in ecological theory relative to that given to competition and predation, and implored the field to rectify this imbalance. While some progress has been made on this front, competition and predation still dominate ecological thinking about interspecific interactions; indeed, the similarities in coverage between May’s 1981 text and contemporary texts are striking. Moreover, empirical evidence continuous to suggest that positive interactions are not uncommon in nature. Is it possible to incorporate positive interactions into standard ecological theory in a more satisfying way? If not, why does empirical and theoretical work lead us to such different conclusions regarding the importance of positive interactions? 2. Prolonged transients and abrupt dynamical changes in spatially extended ecological systems. Spatially extended populations that undergo alternating bouts of reproduction and dispersal are prone to abrupt and surprising dynamical changes. This project seeks to characterize the mathematical genesis of these transients, to articulate the biological conditions under which abrupt dynamical changes are most likely to appear, and to understand how robust these phenomena may be to environmental variation. This is joint work with Derin Wysham and Alan Hastings. 3. Theory for biodiversity - ecosystem function experiments. With the specter of biodiversity loss, enormous effort is being invested in experiments that attempt to elucidate the effects of biodiversity on community and ecosystem processes. These experiments pose a variety of interesting theoretical questions. For one, some experiments assume a single, pre-determined order of extinction, while others assume that assume extinction is random and every species has an equal extinction risk. Other experiments strike a middle ground, assuming extinction is stochastic, but extinction risks are unequal and are possibly correlated with species traits. Can theory provide a framework for linking these different scenarios? This is joint work with Brad Cardinale. 4. Cause-and-effect inferences for pest management data collected outside an experimental context. In many integrated pest management settings, randomized experiments designed to compare different IPM strategies are hampered by limitations of scale. Scientists in economics and biomedical disciplines confront similar inferential problems, and have developed a body of statistical techniques for drawing cause-and-effect inferences from data collected outside an experimental context, where treatment assignment is not random. This project asks if these same techniques can be gainfully applied to IPM data collected from actively managed farms and ranches. This is joint work with Jay Rosenheim and Jay Bancroft. |