Evolution of cooperation in spatially structured populations

Using a spatial lattice model of the Iterated Prisoner's Dilemma we studied the evolution of cooperation within the strategy space of all stochastic s trategies with a memory of one round. Comparing the spatial model with a ra ndomly mixed model showed that (1) there is more cooperative behaviour in a spatially structured population, (2) PAVLOV and generous variants of it ar e very successful strategies in the spatial context and (3) in spatially st ructured populations evolution is much less chaotic than in unstructured po pulations. In spatially structured populations, generous variants of PAVLOV are found to be very successful strategies in playing the Iterated Prisone r's Dilemma. The main weakness of PAVLOV is that it is exploitable by defec tive strategies. In a spatial context this disadvantage is much less import ant than the good error correction of PAVLOV, and especially of generous PA VLOV, because in a spatially structured population successful strategies al ways build clusters. (C) 1999 Academic Press.