Comparative riverscape genetics reveals reservoirs of genetic diversity for conservation and restoration of G reat P lains fishes

We used comparative landscape genetics to examine the relative roles of historical events, intrinsic traits and landscape factors in determining the distribution of genetic diversity of river fishes across the N orth A merican G reat P lains. Spatial patterns of diversity were overlaid on a patch‐based graphical model and then compared within and among three species that co‐occurred across five G reat P lains watersheds. Species differing in reproductive strategy (benthic vs. pelagic‐spawning) were hypothesized to have different patterns of genetic diversity, but the overriding factor shaping contemporary patterns of diversity was the signature of past climates and geological history. Allelic diversity was significantly higher at southern latitudes for C yprinella lutrensis and H ybognathus placitus , consistent with northward expansion from southern P leistocene refugia. Within the historical context, all species exhibited lowered occupancy and abundance in heavily fragmented and drier upstream reaches, particularly H . placitus ; a pelagic‐spawning species, suggesting rates of extirpation have outpaced losses of genetic diversity in this species. Within most tributary basins, genetically diverse populations of each species persisted. Hence, reconnecting genetically diverse populations with those characterized by reduced diversity (regardless of their position within the riverine network) would provide populations with greater genetic and demographic resilience. We discuss cases where cross‐basin transfer may be appropriate to enhance genetic diversity and mitigate negative effects of climate change. Overall, striking similarities in genetic patterns and in response to fragmentation and dewatering suggest a common strategy for genetic resource management in this unique riverine fish assemblage.