Station d'Ecologie Expérimentale du CNRS à Moulis USR2936, 09200 Saint-Girons, France.
Evolution. 2010 May;64(5):1290-300. doi: 10.1111/j.1558-5646.2009.00902.x. Epub 2009 Nov 20.
Aggregative groups entail costs that must be overcome for the evolution of complex social interactions. Understanding the mechanisms that allow aggregations to form and restrict costs of cheating can provide a resolution to the instability of social evolution. Aggregation in Tetrahymena thermophila is associated with costs of reduced growth and benefits of improved survival through "growth factor" exchange. We investigated what mechanisms contribute to stable cooperative aggregation in the face of potential exploitation by less-cooperative lines using experimental microcosms. We found that kin recognition modulates aggregative behavior to exclude cheaters from social interactions. Long-distance kin recognition across patches modulates social structure by allowing recruitment of kin in aggregative lines and repulsion in asocial lines. Although previous studies have shown a clear benefit to social aggregation at low population densities, we found that social aggregation has very different effects at higher densities. Lower growth rates are a cost of aggregation, but also present potential benefits when restricted to kin aggregations: slow growth and crowd tolerance allow aggregations to form and permit longer persistence on ephemeral resources. Thus in highly dynamic metapopulations, kin recognition plays an important role in the formation and stability of social groups that increase persistence through cooperative consumptive restraint.
聚集群体需要克服一定的成本，才能促进复杂社会互动的发展。了解允许聚集形成并限制欺骗成本的机制，可以为解决社会进化的不稳定性提供答案。嗜热四膜虫中的聚集与生长减缓的代价有关，同时通过“生长因子”交换提高了生存的益处。我们通过实验微宇宙研究了在面对潜在的不合作群体的剥削时，是什么机制导致了稳定的合作聚集。我们发现，亲缘识别调节聚集行为，将欺骗者排除在社会互动之外。通过在斑块之间进行远距离亲缘识别，可以调节社会结构，使聚集群体中的亲缘得到招募，而在非社会群体中则产生排斥。虽然先前的研究表明，在低种群密度下，社会聚集有明显的益处，但我们发现，社会聚集在更高的密度下有非常不同的影响。聚集的生长速度较慢是一种代价，但当限制在亲缘聚集中时，也可能带来潜在的好处：缓慢的生长和对拥挤的耐受性使聚集能够形成，并允许在短暂的资源上更长时间的持续存在。因此，在高度动态的复合种群中，亲缘识别在形成和稳定增加生存持久性的社会团体中发挥着重要作用，这种社会团体通过合作性的消费限制来实现。
