River regulation, or the hydrological alteration of flow by dams and diversions, has been implicated as a cause of fundamental changes to downstream aquatic ecosystems. Regulation changes the natural flow regime which may restrict population connectivity and decrease genetic diversity in some species. Since population connectivity and the maintenance of genetic diversity are fundamental drivers of long-term persistence, understanding the extent which river regulation impacts these critical attributes of genetic health is an important goal. Foothill yellow-legged frog (FYLF; Rana boylii ) were historically abundant throughout many western rivers but have declined since the onset of regulation. However, the extent to which FYLF populations in regulated rivers are maintaining connectivity and genetic diversity is unknown. Here we use genetic methods to investigate the impacts of river regulation on FYLF to explore their potential for long-term persistence under continued regulation. We found FYLF in regulated rivers showed striking patterns of isolation and trajectories of genetic diversity loss relative to unregulated rivers. For example, river regulation explained the greatest amount of variance in population genetic differentiation compared with other covariates including geographic distance. Importantly, patterns of connectivity and genetic diversity loss were observed regardless of regulation level but were most prominent in locations with the greatest regulation intensity. Although our results do not bode well for long-term persistence of FYLF populations under current flow regulation regimes, they do highlight the power of genetic monitoring for assessing population health in aquatic organisms.. CC-BY-NC-ND 4.0 International license It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/316604 doi: bioRxiv preprint first posted online May. 13, 2018;
KeywordsRivers, hydropower, flow regulation, genetics, frogs, hydrologic connectivity
SignificanceHydropower is an important source of renewable energy globally, but hydropower generation modifies natural flow regimes and may alter important processes of aquatic ecosystems. Better methods for assessing the long-term impacts of river regulation on aquatic ecosystems are needed. For example, exploring the potential for long-term population persistence in aquatic species under current regulation levels is a key component for conservation management. Our study uses genetic methods to investigate the impacts of river regulation on population health of a river-breeding frog species. We found that populations in regulated rivers showed striking patterns of connectivity and genetic diversity loss relative to unregulated rivers. Our results suggest that changes to current regulation regimes may be needed to promote long-term population persistence.
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