The importance of biotic interactions for demography, niches and geographical ranges of South African Proteaceae (InterNiche)

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A fundamental, yet largely unanswered, question in ecology is how biotic interactions among organisms affect the demographic performance, ecological niches and geographic ranges of species at large spatial scales. Here, we address this question for shrubs of the Proteaceae family from the South African Fynbos biome. We build on a previous project that assembled an extensive dataset on large-scale variation in demography, functional traits and biotic environments, and that developed process-based statistical models which use these data to infer the realized niches of 26 species. The realized niche is the set of environments in which a species can form stable populations in the presence of interacting species. In the present project, we will considerably extend the dataset and the statistical models to address three major questions: (1) how does the interplay between biotic interactions and the physical environment affect large-scale variation in key demographic rates (reproduction and mortality), (2) how do plant functional traits shape biotic interactions and demographic responses to the physical environment, and (3) to what extent do biotic interactions alter the ecological niches and geographic ranges of species. By answering these questions, the project will conduct novel, large-scale tests of foundational ecological concepts and theories. In particular, we will use first principles of demography to quantify the large-scale fundamental niches of species (the set of environments in which a species can form stable populations in the absence of interacting species). We will then contrast fundamental and realized niches to quantify the impact of biotic interactions on the large-scale performance and geographic ranges of species. In summary, this project will yield new insights into the interaction and coexistence of species at biogeographical scales. It will thus make substantial contributions to the understanding of large-scale biodiversity dynamics.