Figure 1.

The five types of dynamics of growth factor production. The evolutionary dynamics of growth factor production depends on how the benefit of the growth factor changes as a function of the fraction of producer cells. The equilibria are found where β(x)−c=0, that is, where β(x) intersects the constant line c (the cost of producing the growth factor; dashed line); the fraction of producers increases if β(x)>c and decreases if β(x)<c; the arrows show the direction of the change. There are five possible types of dynamics: (A) only x=0 is stable; s=0.5, h=0.3, c=0.12. (B) Only x=x_s is stable; s=0.5, h=0.7, c=0.02. (C) Both x=0 and x=x_s are stable; s=0.5, h=0.3, c=0.1. (D) Both x=0 and x=1 are stable; s=0.5, h=0.3, c=0.02. (E) Only x=1 is stable; s=0.1, h=0.3, c=0.02. n=20.