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Aim: A full understanding of the origin and maintenance of β‐diversity patterns in a region requires understanding of: (1) the relationships of both taxonomic and phylogenetic β‐diversity (TBD and PBD, respectively) and their respective turnover and nestedness components with geographical and environmental distances; (2) the relative importance of the turnover and nestedness components of β‐diversity; and (3) the relationships between PBD measures representing different evolutionary depths. Here, we investigate all these aspects of β‐diversity simultaneously for freshwater fishes in North America. Location: North America north of Mexico (hereafter, North America). Taxon: Freshwater fishes. Methods: North America was divided into 360 watersheds. Using two sampling approaches (neighbourhood vs. pairwise), we quantified β‐diversity between fish assemblages using various metrics (representing total, turnover and nestedness components of TBD and PBD, and tip‐ vs. basal‐weighted PBD) and related them to geographical and climatic factors using correlation and regression analyses. Results: Geographical patterns of total TBD and PBD and their components of turnover and nestedness for freshwater fish assemblages among neighbouring watersheds were highly congruent across North America. Geographical patterns of basal‐weighted PBD were generally opposite to those of tip‐weighted PBD. Metrics of β‐diversity were weakly associated with contemporary climatic variables. TBD and PBD were associated strongly to moderately with geographical distances and moderately with climatic distances. The relationships of metrics of β‐diversity to geographical distances were stronger than those to climatic distances in all cases. Main conclusions: Geographical and ecological patterns are highly congruent between taxonomic and tip‐weighted PBD, but those between tip‐ and basal‐weighted PBD are greatly different, suggesting that evolutionary histories have played an important role in shaping β‐diversity. Our study suggests that geographical distance between watersheds is more important than climate similarity in determining β‐diversity between freshwater fish assemblages. [ABSTRACT FROM AUTHOR]

The tropical niche conservatism hypothesis suggests that most groups should be most phylogenetically clustered in cold, dry environments. This idea has been well‐tested in plants and some animal groups, but not for fishes. We assess the geographic patterns of freshwater fish phylogenetic structure and investigate the relationships between these patterns and environmental variables across North America and within two biogeographic realms. Phylogenetic relatedness and diversity of 360 freshwater fish assemblages across North America were quantified with three metrics based on a well‐dated phylogeny, and were related to 15 environmental variables using correlation and regression analyses. Geographically, the data were analyzed for North America as well as for separate biogeographic realms. We found that cold temperatures are the strongest determinant of phylogenetic clustering overall. However, in the arid west, clustering is most pronounced in the driest regions. In eastern North America, phylogenetic clustering increases at higher latitudes, while the reverse is true in western North America. The strongest phylogenetic clustering for freshwater fish assemblages on the continent is found in the most arid, rather than the coldest, climate in North America. Our results highlight that patterns of phylogenetic structure of freshwater fishes in North America are driven by both ecological and evolutionary processes that differ regionally. [ABSTRACT FROM AUTHOR]

Climate is a critical driver of many fish populations, assemblages, and aquatic communities. However, direct observational studies of climate change impacts on North American inland fishes are rare. In this synthesis, we (1) summarize climate trends that may influence North American inland fish populations and assemblages, (2) compile 31 peer-reviewed studies of documented climate change effects on North American inland fish populations and assemblages, and (3) highlight four case studies representing a variety of observed responses ranging from warmwater systems in the southwestern and southeastern United States to coldwater systems along the Pacific Coast and Canadian Shield. We conclude by identifying key data gaps and research needs to inform adaptive, ecosystem-based approaches to managing North American inland fishes and fisheries in a changing climate. [ABSTRACT FROM AUTHOR]

Climate change is a global persistent threat to fish and fish habitats throughout North America. Climate‐induced modification of environmental regimes, including changes in streamflow, water temperature, salinity, storm surges, and habitat connectivity can change fish physiology, disrupt spawning cues, cause fish extinctions and invasions, and alter fish community structure. Reducing greenhouse emissions remains the primary mechanism to slow the pace of climate change, but local and regional management agencies and stakeholders have developed an arsenal of adaptation strategies to help partially mitigate the effects of climate change on fish. We summarize common stressors posed by climate change in North America, including (1) increased water temperature, (2) changes in precipitation, (3) sea level rise, and (4) ocean acidification, and present potential adaptation strategies that fishery professionals may apply to help vulnerable fish and fisheries cope with a changing climate. Although our adaptation strategies are primarily from North America, they have broader geographic applicability to fish and aquatic biota in other jurisdictions. These strategies provide opportunities for managers to mitigate the effects of climate change on fish and fish habitat while needed global policies to reduce greenhouse gas emissions emerge, which may offer more lasting solutions. [ABSTRACT FROM AUTHOR]