Using microcosms to bridge metacommunity theory with natural patterns
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Metacommunties are sets of interacting species embedded in landscapes and interconnected via dispersal. The development of metacommunity theory has greatly outpaced its experimental testing. This situation restricts the feedbacks between theory and natural systems, hindering the development of useful theory and limiting application of theory to natural patterns. My dissertation aims to accelerate the testing of metacommunity theory using three microcosm experiments ranging from highly to more loosely constrained. The first experiment implemented a competition-colonization tradeoff between two strains of bacteria and tested if the tradeoff produced the expected patterns of coexistence and ecosystem function. Generally, the results conformed closely to theoretical expectations, though high stochasticity limited coexistence. The second experiment utilized multi-trophic protist communities to test if assembly history followed by complete mixing can produce situations where one community replaces another. Results indicate that community replacement can occur under mixing, though it may be buffered by trophic structure. The third experiment tested the ability of variance partitioning to attribute landscape patterns to process in a one-predator two-prey system. Results indicate that both predators and dispersal can generate similar spatial patterns. Distinguishing between the two requires explicitly incorporating the predator into the partition. In summary, each of these three experiments reinforces aspects of existing theory while illuminating new paths for future theoretical and empirical exploration.