The assembly and maintenance of biodiversity in multitrophic communities

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Global changes driven by continuously growing human populations and activities are causing a global reshuffling of biodiversity. Communities of animals, plants and microbes are rapidly changing in response to anthropogenic pressure, resulting in biodiversity gains and losses. To predict and manage biodiversity in a changing world, it is imperative to understand the factors affecting community assembly (how species come together) and biodiversity maintenance (how biodiversity persists through time). Predictions of current and future biodiversity often focus on the process of abiotic selection, while often neglecting the importance of biotic selection. Abiotic selection results from a a match between local climate, or other abiotic variables, and a species' ability to tolerate these conditions. Biotic selection relates to whether species attract or repel each other. Abiotic and biotic selection thus dictate which mix of species can persist together in one place. The exact mechanisms by which biotic selection influences the build up of communities, however, are still being investigated. Biotic selection can operate within a trophic level (plants excluding each other via competition) or between trophic levels (plant flowers that are incompatible with a pollinator). The influence of trophic and non-trophic interactions on communities and biodiversity are rarely considered jointly. To move forward, biodiversity scientists must develop a theory of ecological community assembly that integrates trophic and non-trophic interactions. Network approaches are used to describe complex patterns of biotic interactions in multitrophic communities (communities with more than one trophic level). An ecological network is a pattern describing pairwise interactions between species occupying different trophic levels. There is great variation in the structure of ecological networks observed in nature, but the causes of such variation are poorly understood. Our research group developed a conceptual and methodological framework to further our understanding of processes underpinning the assembly and maintenance of biodiversity in multitrophic communities (i.e., ecological networks). We also developed the expertise and technology to describe the structure of complex ecological networks across a variety of natural systems: from plant-microbe, to plant-herbivore and plant-pollinator networks. The goal of the proposed research program is to build on recent theoretical, methodological and technological developments to determine the processes shaping biodiversity. We will accomplish this by combining field experiments and environmental DNA sequencing to identify the "rules" that shape plant-pollinator networks and their resilience to human perturbations. Results from these projects will have a significant impact on our ability to predict future changes in insect pollinator diversity, which is essential to mitigate the loss of the important services they provide to humans.