Figure 1.

Conceptual model of natural selection on flowering phenology in the context of anthropogenic climate change. (a) Prior to industrialization: stabilizing selection could have favoured intermediate flowering time owing to seasonal constraints on growth and reproduction. (b) Contemporary conditions: climate change causes growing seasons to begin earlier, shifting the fitness landscape and resulting in directional selection for earlier flowering. (c) Future conditions: under continued warming, natural populations with limited genetic variation could fall far from the fitness optimum, have severely depressed fitness, and risk extinction. Further details are available in electronic supplementary material, S1.