Assessing the threats of climate change to the distribution and functional diversity of a continental freshwater fish assemblage

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Global climate change is considered a major threat for biodiversity. Freshwater ecosystems are expected to be highly vulnerable to warming climates and changing precipitation patterns, accompanied by multiple anthropogenic stressors. Due to their substantial variation in size freshwater ecosystems harbour geographically highly uneven yet often highly concentrated species richness that is exceptionally susceptible to global change: while freshwater ecosystems cover less than 1% of the Earth's surface, they contain approximately 10% of all described species. Moreover, freshwater ecosystems are fragmented habitats, and especially the combination of multiple stressors acts as a driver for a high vulnerability of species inhabiting these unique hotspots. Identifying the most diverse and susceptible locations for freshwater species for spatial conservation prioritisation is thus of high priority. Combined with trait information, the functional diversity of assemblages can be quantified and species distinctness explicitly included for conservation prioritization.The proposed project aims to undertake such an assessment addressing multiple dimensions of biodiversity in the context of climate-change impacts for a whole continental freshwater assemblage, the fish fauna of North America. With 1050 species the region is highly diverse and moreover has an exceptionally strong data situation. This will allow me to first build a solid baseline prediction and understanding of current-day fish distributions using state-of-the-art Bayesian spatial modelling approaches and newly developed high-resolution environmental layers characterizing stream conditions. These predictions combined with climate change projections scaled to the stream level will allow me to assess in detail current day vs. future centres of richness and potential changes to species geographic ranges. By extending existing trait datasets and linking it to spatial species predictions I will address basic biogeographic questions about the North American fish fauna and specifically assess the potential discrepancy between patterns of species richness and functional diversity. Finally, I will evaluate the potential changes and loss of different biodiversity facets by relating projected range changes to species functional distinctness under climate change scenarios.The proposed work will provide a first continental-scale biogeographic and explicitly spatial climate-change assessment of an important group of freshwater organisms. By applying latest spatial and environmental modelling techniques and linking in ancillary species information, it has the potential to lay a useful methodological groundwork and address several questions of general interest. Freshwater species remain notoriously understudied, and the work may offer a useful blueprint or point of comparison for other regions (e.g. European fish) or taxa.