The ecology and evolution of biodiversity in natural metacommunities

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A fundamental goal motivating community ecology research is to understand how biodiversity is maintained in space and time. In the early 2000s, community ecology was criticized as lacking mechanistic power and being too wrought with contingency. In response, modern community ecology emphasizes two approaches: (1) mechanistic experiments designed to pinpoint ecological processes, rather than infer them from descriptive patterns, and (2) recognizing that communities are linked by dispersal to form a regional network, or "metacommunity", offering a general predictive framework to understand ecological outcomes. However, experimental tests of metacommunity theory in actual natural metacommunities are exceptionally scarce given the difficulty of manipulating dispersal in the field, thus presenting one of the greatest knowledge gaps facing ecology today. My lab studies the ecology and evolution of biodiversity in a metacommunity of annual grassland plants in Northern California. Annual plants are ideal to test metacommunity processes in the field given that individuals and whole communities can be translocated via seed, simulating dispersal. In this system, I have shown that limited dispersal prevents species from accessing suitable habitat patches, and that the spatial scales at which dispersal limitation manifests is determined by environmental structure. However, we do not know how stable this outcome is through time or its consequences for diversity at community/metacommunity scales. We will use manipulative field experiments to test the following predictions that form the basis of three research objectives: 1.Dispersal causes species' observed occupancy patterns to mismatch patterns that would be expected if species were perfectly sorted into suitable portions of environmental gradients (allowing tests of where and why mismatches occur) 2.Dispersal is non-random, occurring directionally from some patches to others based on how seed dispersal vectors (e.g., animals, hydrology) connect habitat patches, affecting community richness and composition 3.Because dispersal causes interspecific competitors to overlap in some habitat patches and not others, dispersal histories direct the evolution of competitive interactions and persistence The proposed objectives bridge fundamental gaps between metacommunity ecology, evolutionary ecology, and landscape ecology, testing the real-world feasibility of metacommunity predictions, advancing basic theory. Basic theory can then inform conservation action (e.g., at what spatial scale should landscapes be managed to preserve regional processes?), both in my study system and in others, such as Canadian forests, where ecological dynamics are slower to observe (e.g., long generation times) or diversity less amenable to manipulation. Ultimately, we will provide novel evidence of how and why ecological processes interact across scales in natural systems, driving evolution and the scale-dependence of biodiversity.