Capacity of Adaptive Responses by Salmon to Buffer Effects of Climate Change

To evaluate the capacity of salmon to adaptively respond to climate change, we developed an individual-based, eco-evolutionary model that incorporates both evolution and phenotypic plasticity (and allows for evolution of reaction norms).  The model includes two environments (“stream” and “ocean”) and migration between them.  The user can specify several heritable traits (and correlations among them), the elevation and slope of reaction norms, the nature of density dependence, intrinsic population growth rates, the magnitude of random and directional environmental variation, and other features.  The model tracks population abundance, additive genetic variance, and mean trait values over time in a single isolated population or two populations connected by migration.  We use the model to evaluate 1) the importance of cue reliability for adaptive phenotypic plasticity, and the consequences for persistence if cue reliability degrades under climate change; 2) the capability of salmon to rapidly evolve migration timing to track directional changes in flow and temperature in the range predicted by current climate-change scenarios; 3) prospects for genetic rescue of increasingly maladapted populations by immigrants from other populations.