Causes and consequences of spatio-temporal variation of species interactions at the community scale

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Interactions between species are key both to the properties of ecosystems, and to the well-being of human populations. Pollination of agricultural crops by insects allows the provision of food, grazing of algae by sea urchins prevents algal blooms in coastal areas, and the presence of predators keep the population size of their preys in check. Yet, it has often been assumed that interactions between species are constant, or in other words, that the same two species will interact in the same ways in different contexts. Recent analysis of field observations show that this is not the case; much in the same way that species vary in their geographical range, so too do interactions. My research program seeks to provide explanations to this variation, and building on this new knowledge, to establish predictions about how we expect ecosystem properties to change in time or space. One of the most important predicted output of this research program is the ability to predict, based on measured data, the probability that two species will interact in a given environment. I will use tools from the relatively new field of computational ecology, which builds on high-performance simulations and statistical methods designed to analyse extremely large datasets, to address these questions. Although my research activities are theoretical, I will work in close association with empirical scientists. This collaboration will allow me to have access to high-quality observations backed by robust knowledge of the natural history of the different systems. This close collaborations will also ensure that the theoretical advances I will make, and in particular the new tools and methods I will develop, are grounded in the questions and observations of researchers with first-hand knowledge of natural systems. In particular, I will make sure that all the students I train have the opportunity to spend some time working on an empirical system, so that they can contribute to bridging the gap between theoretical and empirical science. In addition to providing new mechanisms and theoretical propositions for fundamental scientists to build upon, I expect that my work will appeal to managers and stakeholders, as it will provide a new way to forecast the structure of ecological communities. This will allow better predictions of the effects of species invasions and environmental changes, for example, on ecosystem properties in need of preservation.