1. Departments of Zoology and Mathematics, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada

Correspondence to: Christoph Hauert Correspondence and requests for materials should be addressed to C.H. (Email: hauert@zoology.ubc.ca).

Abstract

Understanding the emergence of cooperation is a fundamental problem in evolutionary biology¹. Evolutionary game theory^{2, 3} has become a powerful framework with which to investigate this problem. Two simple games have attracted most attention in theoretical and experimental studies: the Prisoner's Dilemma⁴ and the snowdrift game (also known as the hawk–dove or chicken game)⁵. In the Prisoner's Dilemma, the non-cooperative state is evolutionarily stable, which has inspired numerous investigations of suitable extensions that enable cooperative behaviour to persist. In particular, on the basis of spatial extensions of the Prisoner's Dilemma, it is widely accepted that spatial structure promotes the evolution of cooperation^{6, 7, 8}. Here we show that no such general predictions can be made for the effects of spatial structure in the snowdrift game. In unstructured snowdrift games, intermediate levels of cooperation persist. Unexpectedly, spatial structure reduces the proportion of cooperators for a wide range of parameters. In particular, spatial structure eliminates cooperation if the cost-to-benefit ratio of cooperation is high. Our results caution against the common belief that spatial structure is necessarily beneficial for cooperative behaviour.

1. Departments of Zoology and Mathematics, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada

Correspondence to: Christoph Hauert Correspondence and requests for materials should be addressed to C.H. (Email: hauert@zoology.ubc.ca).

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