be expected, curves for $t_1$ are below curves for $t_2$. Another important feature is that the final fraction of cooperators for ordered networks is always larger than what is obtained in completely random networks. Even though this seems to confirm the impression that clustering is beneficial to cooperators, it must be noticed that many curves are not monotonic with $C$, as for example, all curves corresponding to random ring networks.

Another interesting feature to notice is that, for ring networks the addition of a very small amount of disorder causes an abrupt decrease in the steady fraction of cooperators. This happens because of the one-dimensional nature of the ring: rewiring very few links at each side of a cooperation cluster can be very effective in stopping its expansion. When more links are rewired the dimensionality of the system begins to increase and cooperators clusters find new directions to expand.

For all values of $C$ curves for random ring networks are always below those for random lattice networks, for the same values of $t$. This is probably related to the lower dimensionality of the substrate of the random ring network that may have an influence even for high values of the 