Dams and Introduced Species Drive Patterns of Environmental Adaptation in an Iconic but Imperiled Coldwater Fish (Brook Trout, <i>Salvelinus fontinalis</i> )

) with a long history of negative impacts from human-induced stressors and now increasingly affected by climate change. We developed a new restriction site-associated DNA capture panel to genotype 3297 SNPs in over 2200 brook trout from 55 waterways across the Lake Superior basin. We used partial redundancy analyses to identify over 300 SNPs potentially involved in adaptation. Our study is among the first to implicate both movement barriers and introduced species in shaping environmental adaptation, along with climate. System-specific variables for introduced Pacific salmon and stream fragmentation caused by movement barriers exhibited some of the strongest associations with genetic variation, highlighting the role that dams and introduced species-features characteristic of the Great Lakes and much of North America-may play in shaping adaptation in native fishes. We also identified temperature and stream flow as strongly associated with putatively adaptive genetic variation, as reported in other studies. Importantly, these insights were possible given locally derived environmental information, which we analyzed alongside widely accessible broad-scale climate data. Finally, by calculating adaptive index and genomic offset, we identified areas where brook trout appear heterogeneously adapted across the landscape and where locally adapted genotypes may be prone to disruption from climate change. Our findings offer novel insights into environmental adaptation in brook trout and foundational knowledge for developing management plans that conserve the adaptive capacity of populations already experiencing changing conditions.