CoevSim

A visualizer of spatially distributed coevolution among three species. The three engage in a rock-paper-scissors dynamic: pairwise interaction outcomes are determined by phenotypic matching, so each species tracks the next around the cycle while fleeing the previous one, and none can win. The trait value of each species is the red, green, and blue content of a pixel, and the community at each spatial location is summarized by the resulting RGB color.

Adjust relative selection strengths to see emergent color palettes, and relative dispersal abilities to see emergent spatial patterns. Two further forces are off by default: stabilizing selection pulls each species toward its own spatial optimum (switch the view to Optima to see where those sit), and drift perturbs each population by sqrt(G/Ne) per generation, which can be made to strengthen toward the range margin where Ne is small.

Controls:

• Sliders for dispersal, coevolution, stabilizing selection, and drift
• Tap/click the lattice, or the play button, to pause and resume
• Step advances a single generation
• -/+ coarsen or refine the lattice
• Random, At optima, and Uniform reseed the field
• Press h to hide or show the sliders

Keyboard shortcuts (space, s, r, h, [ , ]) need the frame focused — click it once first.