EAGER: Explaining species coexistence from first principles of ecology

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The coexistence of species has long fascinated ecologists. It seems reasonable to think that one species should be better at functioning in the environment than others and become dominant, however, this is not always the case in nature. Plant species commonly coexist in natural systems in large numbers, and this diversity contributes to many important ecosystem services, including soil retention, the pollination of nearby crops, and carbon storage. Our ability to predict species coexistence is limited. Many theories have been developed to explain why plant species might coexist under the particular circumstances we find them in, but none is able to predict that coexistence directly from first principles of ecology, i.e. the fundamental mechanisms that govern ecosystem function universally. In order to predict how ecosystems around the globe will react to, and thus further affect, environmental variability, we need to understand them on this fundamental level. New theoretical models will be developed, and will rely on expanded first principles of ecology. The research will result in the training of graduate students as well as a postdoctoral researcher in mathematical ecology. Additionally, the research will engage and train high school teachers in hypothesis testing and research.This research will investigate the role of three specific mechanisms in generating species coexistence: successional dynamics (the changing environment due to regrowth of a plant community that follows a disturbance event), plant-herbivore interactions (the co-evolution of plants and their natural enemies), and limitations to evolutionary optimization (the reality of small sample sizes and changing environments that keep plants from evolving into the perfect species for a specific environment). The research will build simple models of plant interactions with one another and their environment. This will incorporate only assumptions that reflect the first principles of ecology: (1) that individual growth rates and population sizes are generally limited by resources, (2) that there is variation in the input rate of resources to environments, (3) that species depend on other trophic levels, driven in their own right by strong positive biological feedbacks, (4) that there are hard physical and/or physiological constraints on species, and (5) that individuals that have more offspring than their neighbors better resemble the traits of individuals in future generations (individual-based competition or evolution by natural selection). The research will test whether and how species coexistence may arise from these principles. Specific predictions of coexistence will be compared with data wherever possible.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.