Ecological and evolutionary dynamics

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One of the most striking features of natural ecosystems is their great diversity of species. This diversity can vary among sites and over time. Less obvious, but equally striking, is evolutionary diversity: temporal and spatial variation in phenotypes and gene frequencies. How is this variation generated and maintained? These questions are of fundamental interest for basic ecological and evolutionary research, and also underpin the conservation of biodiversity. At a basic level, we know the answer: the abundance of any type of organism just depends on the rates at which it gives birth, dies, and moves between sites (and on longer timescales uniquely-evolutionary forces like speciation come into play). But working out the details is extremely difficult, since rates of birth, death, and movement can vary greatly in space and time and depend on many factors.****My research addresses how the fundamental processes of birth, death, and movement generate patterns in biodiversity using model systems in which the rates of these processes can be measured and manipulated.  My proposal describes three sets of projects addressing different questions: (1) How do demographic and environmental stochasticity interact with deterministic forces to drive population and community dynamics? I propose to answer this question with laboratory microcosm communities comprised of fast-growing protists and bacteria. This system allows me to directly manipulate the strength of demographic stochasticity and other factors, manipulations that are impossible in most other systems. (2) Can temporal environmental variation maintain genetic diversity as effectively as spatial variation? I propose to answer this question by testing for local adaptation of lake bacteria to spatial and temporal variation in water chemistry, using a novel protocol I have developed to transplant bacteria in time as well as space. (3) How do species interactions affect local adaptation and species distributions along environmental gradients? I propose to examine how the biotic environment (neighboring plants) affects how alpine plants adapt to their harsh abiotic environment, thereby affecting the maintenance of adaptive genetic variation along elevational gradients and determining species' elevational range limits. ****The proposed research is hypothesis-driven. It combines new approaches to classic problems with direct attacks on problems that have not previously been addressed. The results will improve our understanding of stochasticity, provide the first field data on whether environmental fluctuations maintain genetic diversity, and resolve open questions about the ecological and evolutionary determinants of range limits. Besides contributing to fundamental understanding, the proposed work will provide training for 7 graduate students and provide research experience for at least 13 undergraduates.**