Fig 3. Pattern formation under competing forms of directed migration.

(A), (C) Cooperator aggregation results in smooth patterns for small A_C, which are suppressed by increasing A_D, R_C. However, for larger A_C the positive feedback between aggregation and densities of cooperators dominates. This eliminates defectors and gives rise to discontinuous distributions. Consequently, directed migration triggered by defector densities through A_D or R_C no longer matters. (B), (D) Spreading defectors, R_D, also promote pattern formation but maintain smooth patterns, while increases in A_D, R_C again suppress them. Parameters: Multiplication factor r = 2.4, D_D = 0.5 > D_C = 0.1 to observe smooth patterns for A_C; snapshots taken at t = 2000; Gaussian initial configuration without noise. Other parameters as in Fig 1.