We study an Iterated Prisoner's Dilemma game in which players are positioned on a lattice and interact with their near neighbours. Periodically the strategy at every site is replaced by the most successful one of its neighbours and itself. We search for collective behaviour acid find dynamically stable ''communities'' with three or even four distinct strategies coexisting. Multi-strategy ''communities'' are more immune to invasion by other strategies than are homogeneous states of the individual members. An explanation of this phenomenon is provided. [References: 8]
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