Two illustrative runs of the individual-based simulation, showing allele frequencies at the recognition locus (coloured lines) and behaviour locus (black line). Black dots mark the recognition allele with the highest frequency among individuals with at least one cooperative allele. Panel A: In this run, cooperation eliminated recognition locus diversity. The figure assumes the following parameter space: x = 6, b = 6, c = 1, m = 0, N = 6, k = 5, r = 0.05, d = 0.1, μ = 10-5, h = 1 and 2-allele matching, as in the centre of Figure 2B. Panel B: The cooperative allele invaded without depleting recognition locus diversity. The parameter space is the same as before except b = 3 and m = -1, as in the bottom left of Figure 2B.