Climate change, hydrology, and fish morphology: predictions using phenotype-environment associations

Phenotype-environment associations (PEAs) describe relationships between the mean phenotypes of a set of populations and the environmental values of the areas in which they inhabit. We show how these PEAs can be used to determine the ability of populations to adapt to future environmental changes, using relationships between fish body shape and stream flow rates as an example. First, we establish that fish in high-flow habitats have more streamlined body shapes than those in low-flow habitats. Then, using future estimates of flow rates obtained from landscape hydrologic models, we predict body shapes of stream fish in the year 2055. Lastly, we use simulations based on a quantitative population genetics model to determine each fish population's ability to alter its phenotype to the predicted body shape in 2055. While some fish populations were predicted to be able to reach the predicted body shape, others were identified as vulnerable to changing flow rates and may need human assistance to persist into the mid-century. The simulations introduced here combine correlative and mechanistic methods to predict future adaptation to environmental change and are applicable to a wide range of taxa.