Is urban streams are eco-evolutionary drivers of freshwater fish invasion?

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Biodiversity, especially in freshwater habitats, has suffered severe depletion since the onset of the industrial period. Habitat degradation and invasive species are identified as the two main causes for this decline, but their effects are context-dependent. Some regions act as invasion hotspots, where invasive species are disproportionately abundant. Invasion hotspots are suggested to be more prevalent in disturbed habitats, notably urban and suburban environments. Whereas invasion biology recognizes that invasive species could benefit from urban environments for the initial introduction, establishment and secondary dispersal, mechanisms of this facilitation remain to be better described. Ecologically, two alternative hypotheses are suggested, where either decrease of competition by disturbance-intolerant species or increase of reliance on ecological opportunities (e.g. food resources, habitats) in disturbed habitats by urban-tolerant invasive species. From an evolutionary point of view, growing evidence is pointing toward urban-induced evolution, fueled by said ecological interactions, as a promoter of invasion. All examples of urban evolution of invasive species, however, have been developed in plants, mammals or avian model species; fishes remain uncommon in this field. Hence, establishing if and how urban streams are hotspots of invasion and if they act as an evolutionary driver for invasion is crucial to better understand invasion dynamics, decrease invasion potential and improve cities planning. In this 5-years research program, I will aim to assess the ecological mechanisms resulting in invasive fish prevalence in an increasing gradient of urbanization, to analyze the context-dependent variability of direction and magnitude of the intra- and inter-specific responses of the ecological niche (e.g. trophic and thermal) and vital rates (e.g. growth rates and condition) in communities subjected to disturbance and to find evidence of urban-induced evolution of physiological traits (metabolic rates) adapted to disturbed habitats. By applying an integrative ecology framework, which will combine community ecology, biogeochemistry (stable isotopes analysis) and field-based respirometry we will provide insights into fundamental mechanisms at play in biological invasion and how adaptive management of cities could mitigate invasion opportunities. Identification of how cities' components (e.g. riverbank vegetation, water management, land-uses) increase the prevalence of invasive species in an urban stream will guide managers for promotion of biodiversity conservation in overlooked habitats providing valuable ecosystem services.