Fig. 4.

Conceptual illustration of how dispersal and the evolution of environmental (env.) optima independently and interactively act to maintain biodiversity in changing environmental conditions. A shows the distribution and abundance of 3 species spanning a climate gradient (e.g., warm to cold). Mean position is shown by vertical dashed lines. Each species is locally adapted to a different part of this gradient as indicated by the warmth of the color of the curves. B–D show hypothetical scenarios after the environment has changed. In B, with dispersal but no evolution of environmental optima, the species persist by shifting upwards (spatial insurance). In C, with evolution of environmental optima but no dispersal, the species persist by adapting to the changed conditions (change in color, evolutionary rescue), but do not shift their ranges. In D, with both dispersal and evolution, the 2 outer species evolve faster than the middle species, holding on to their initial trailing edge through adaptation but expanding on their leading edge through dispersal (monopolization). By monopolizing the landscape, they drive the middle species extinct (dashed curve). E shows how dispersal and the evolution of environmental optima each allow for species persistence via spatial insurance and evolutionary rescue, respectively (based on Fig. 2A). But together they can lead to monopolization effects, which can reduce biodiversity in changing environments.