Explaining how the stability of cooperative systems is maintained has been one of the central problems in both biology and social science since Charles Darwin and Adam Smith. Popular theories have shown that the initial relatedness coefficient between the involved partners is sufficient to maintain the cooperative interaction, and that this initial relatedness coefficient between the partners can be created by either genetic similarity, mutual reciprocity, inter-group competition, or any other mechanisms that creates a positive fitness correlation. However, an increase in the cooperative actors, which has a positive feedback on the recipient in a cooperative interaction, will also increase their competition with the recipient if the local resource or space is limited. Then, the cooperative actors must compete with the recipient after the common resource is saturated, which is one of the most famous theoretical dilemmas, the “commons tragedy”.

Classical theories argued that self restraint or spatial heterogeneity (restraint) will prevent direct conflict between the cooperative actors and the recipient that results from the increase in the partners. However, Rui-Wu Wang (Kunming Institute of Zoology, CAS) et al. found that the self restraint or spatial heterogeneity (restraint) might not be credible to maintain the stable cooperation between the interacted partners, exemplified with one of most famous inter-specific cooperation of fig-fig wasp mutualism. Their research found that the interference competition among the fig wasps will constrain the common resource utilization such keeping the common resource utilization unsaturated, and therefore stabilized the cooperation between fig and fig wasps. The empirical data evidence published in PLOS ONE in 2009 (PLoS ONE4(11): e7802), and it was recommended by Faculty of 1000 Biology http://f1000biology.com/article/id/1282068. The theoretical model on above idea published in Science China: Life Science in 2010 (53: 139-149).