Community structure inhibits cooperation in the spatial prisoner's dilemma

The origin of evolutionary cooperation among individuals remains an unsolved issue across several disciplines; especially, the relation between the population structure and the emergence of cooperation is the key of the issue. Community structure is ubiquitous in social and biological networks. It is not clear until now whether the community structure promotes or inhibits cooperation. By defining the common neighbor coefficient of a network, the iteration dynamics of the prisoner's dilemma game indicates that smaller value of the common neighbor coefficient of a network promotes cooperation in statistical significance for the prisoner's dilemma game. Analyses show that the community networks usually have larger value of common neighbor coefficient than the ER random networks with the same number of nodes and edges, which shows that the community structure usually inhibits cooperation in the spatial prisoner's dilemma game.