Figure 3. Threshold adhesiveness value $z^{*}$ required for the evolution of increased adhesion.

In the case of group formation by attachment, the theoretical value of $z^{*}$ in the limit of infinite $T$ is $z^{*}=2c∕b$, as demonstrated in Section 4.1. Analytical thresholds (full lines) as well as numerical estimations (circles) are displayed for small ($20$) and large ($100$) values of $T$. As $T$ decreases, threshold values decrease too because of enhanced direct benefits. Numerical results are consistent with analytical predictions. Error bars indicate the variability—associated with the finite size of the population—in the estimation of the threshold across multiple computations of the aggregation process.

DOI: http://dx.doi.org/10.7554/eLife.08595.005