Genetic differences in plasticity across environmental scales determine fitness along an ecological gradient

When populations suffer reduced fitness in novel environments, genotypes with less deleterious forms of plasticity could aid persistence by reducing the severity of fitness declines. However, we know little about how plasticity allows different genotypes track environmental variation to determine population persistence along ecological gradients, particularly as environments become novel. We transplanted numerous clones of 19 genotypes of a Sicilian daisy, Senecio chrysanthemifolius , at four elevations on Mt Etna. We estimated fitness at native and novel elevations, and quantified leaf plasticity both among and within elevations. Compared to genotypes with higher fitness within the native range, genotypes with higher fitness at the novel elevation showed lower variance in fitness, lower plasticity across elevations, but greater plasticity within elevations. Our results suggest there are genotypes hidden in a population whose plasticity better tracks novel environmental variation at fine and coarse scales, which will be crucial for population persistence under rapid environmental change.