Reeve H Kern, Hölldobler Bert
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
Proc Natl Acad Sci U S A. 2007 Jun 5;104(23):9736-40. doi: 10.1073/pnas.0703466104. Epub 2007 May 21.
Surveys of insect societies have revealed four key, recurring organizational trends: (i) The most elaborated cooperation occurs in groups of relatives. (ii) Cooperation is typically more elaborate in species with large colony sizes than in species with small colony sizes, the latter exhibiting greater internal reproductive conflict and lesser morphological and behavioral specialization. (iii) Within a species, per capita brood output typically declines as colony size increases. (iv). The ecological factors of resource patchiness and intergroup competition are associated with the most elaborated cooperation. Predictions of all four patterns emerge elegantly from a game-theoretic model in which within-group tug-of-wars are nested within a between-group tug-of-war. In this individual selection model, individuals are faced with the problem of how to partition their energy between investment in intercolony competition versus investment in intracolony competition, i.e., internal tugs-of-war over shares of the resources gained through intergroup competition. An individual's evolutionarily stable investment in between-group competition (i.e., within-group cooperation) versus within-group competition is shown to increase as within-group relatedness increases, to decrease as group size increases (for a fixed number of competing groups), to increase as the number of competing groups in a patch increases, and to decrease as between-group relatedness increases. Moreover, if increasing patch richness increases both the number of individuals within a group and the number of competing groups, greater overall cooperation within larger groups will be observed. The model presents a simple way of determining quantitatively how intergroup conflict will propel a society forward along a "superorganism continuum."
对昆虫群落的调查揭示了四个关键的、反复出现的组织趋势：（i）最精细的合作发生在亲属群体中。（ii）在群体规模较大的物种中，合作通常比在群体规模较小的物种中更精细，后者表现出更大的内部生殖冲突以及较少的形态和行为特化。（iii）在一个物种内，随着群体规模的增加，人均繁殖产量通常会下降。（iv）资源斑块性和群体间竞争的生态因素与最精细的合作相关。所有这四种模式的预测都巧妙地源自一个博弈论模型，其中群体内部的拔河比赛嵌套在群体间的拔河比赛之中。在这个个体选择模型中，个体面临着如何在群体间竞争投资与群体内竞争投资之间分配能量的问题，即关于通过群体间竞争获得的资源份额的内部拔河比赛。结果表明，随着群体内部亲缘关系的增加，个体在群体间竞争（即群体内部合作）与群体内竞争之间进化上稳定的投资会增加；随着群体规模的增加（对于固定数量的竞争群体）会减少；随着斑块中竞争群体数量的增加会增加；随着群体间亲缘关系的增加会减少。此外，如果斑块丰富度的增加既增加了群体内个体的数量，也增加了竞争群体的数量，那么在更大的群体中将会观察到更高的总体合作水平。该模型提供了一种简单的方法来定量确定群体间冲突将如何推动一个社会沿着“超有机体连续统”向前发展。
