不相关个体之间合作的演化对于社会科学和自然科学领域的研究人员来说都是一个谜。更深了解这一现象的一个可能的障碍是，理论工作者和实验工作者有各行其是的倾向。Bshary等人通过将博弈理论模拟方法、野外观测和实验验证在一项关于合作现象的一个迄今尚未有人探索过的问题的研究中结合起来，从而避免了理论与实验的脱离，而他们所研究的这个问题是名为“半拟隆头鱼”的“医生鱼”（或称“清洁鱼”）与它们的客户鱼的稳定雌雄对之间的清洁互助关系。
理论预测，两个服务提供者应当比单个服务提供者向其客户提供更高质量的服务，只要它们相互合作就行。野外观测和实验都证实了该模型预测。一对“医生鱼”成功的关键是这样一个事实：当一个清洁者从其客户身上吃掉皮外寄生虫时，另一个可继续进行其所喜欢的欺骗行为，即吃其客户的粘液，与此同时仍可保证客户满意。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 455, 964-966 (16 October 2008) | doi:10.1038/nature07184
Pairs of cooperating cleaner fish provide better service quality than singletons
Redouan Bshary1, Alexandra S. Grutter2, Astrid S. T. Willener1 & Olof Leimar3
1 University of Neuchatel, Department of Zoology, Rue Emile-Argand 11 Case postale 158, 2009 Neuchatel, Switzerland
2 University of Queensland, School of Integrative Biology, St Lucia, Queensland 4072, Australia
3 Stockholm University, Department of Zoology, SE-10691 Stockholm, Sweden
Service providers may vary service quality depending on whether they work alone or provide the service simultaneously with a partner. The latter case resembles a prisoner's dilemma1, 2, 3, 4, in which one provider may try to reap the benefits of the interaction without providing the service. Here we present a game-theory model based on the marginal value theorem5, which predicts that as long as the client determines the duration, and the providers cooperate towards mutual gain, service quality will increase in the pair situation. This prediction is consistent with field observations and with an experiment on cleaning mutualism, in which stable male–female pairs of the cleaner wrasse Labroides dimidiatus repeatedly inspect client fish jointly. Cleaners cooperate by eating ectoparasites6 off clients but actually prefer to cheat and eat client mucus7. Because clients often leave in response to such cheating, the benefits of cheating can be gained by only one cleaner during a pair inspection. In both data sets, the increased service quality during pair inspection was mainly due to the smaller females behaving significantly more cooperatively than their larger male partners. In contrast, during solitary inspections, cleaning behaviour was very similar between the sexes. Our study highlights the importance of incorporating interactions between service providers to make more quantitative predictions about cooperation between species.
