Macroecology of temperate riverine ecosystems

Macroecology seeks to understand processes underlying biodiversity patterns at large spatiotemporal scales. Aided by increases in publicly available datasets, macroecologists have made substantial progress towards these aims in recent decades. However, much of this knowledge comes from terrestrial habitats, with comparably fewer macroecological studies in freshwaters. Freshwater environments are interesting contexts for macroecological research owed to high biodiversity, particularly in ectothermic taxa that may be disproportionately threatened by global change. Therefore, large scale approaches will be necessary to adequately assess risks posed to these systems by regional to global anthropogenic stressors. This dissertation leverages recently available datasets to advance the field of freshwater macroecology. We use data-intensive analyses and syntheses to test and evaluate hypothesized mechanisms underlying patterns in freshwater biodiversity, biomass, and phenology. We synthesize freshwater phenology literature to identify prevalent abiotic and intrinsic drivers of phenology regimes and use this information to provide recommendations for more robust assessments of phenological change in freshwaters. We assess mechanisms underlying the biodiversity-ecosystem functioning relationship in riverine stream fish assemblages and assess how non-native species introductions can affect this relationship. We conduct a survey and synthesis of contemporary freshwater community science sampling efforts to inform where freshwater macroecologists can leverage these emerging data sources and identify sampling and participation gaps which could be prioritized by novel sampling efforts. We unify processes underlying patterns in stream fish body size across biological scales to overcome discrepancies created by prior data limited research. This dissertation fills knowledge gaps in freshwater macroecology and provides novel lines of inquiry to be explored by future research efforts.