Data from: Does cooperation mean kinship between spatially discrete ant nests?

Eusociality is one of the most complex forms of social organization, characterized by cooperative and reproductive units termed colonies. Altruistic behavior of workers within colonies is explained by inclusive fitness, with indirect fitness benefits accrued by helping kin. Members of a social insect colony are expected to be more closely related to one another than they are to other conspecifics. In many social insects, the colony can extend to multiple socially connected but spatially separate nests (polydomy). Social connections, such as trails between nests, promote cooperation and resource exchange, and we predict that workers from socially connected nests will have higher internest relatedness than those from socially unconnected, and noncooperating, nests. We measure social connections, resource exchange, and internest genetic relatedness in the polydomous wood ant Formica lugubris to test whether (1) socially connected but spatially separate nests cooperate, and (2) high internest relatedness is the underlying driver of this cooperation. Our results show that socially connected nests exhibit movement of workers and resources, which suggests they do cooperate, whereas unconnected nests do not. However, we find no difference in internest genetic relatedness between socially connected and unconnected nest pairs, both show high kinship. Our results suggest that neighboring pairs of connected nests show a social and cooperative distinction, but no genetic distinction. We hypothesize that the loss of a social connection may initiate ecological divergence within colonies. Genetic divergence between neighboring nests may build up only later, as a consequence rather than a cause of colony separation.

真社会性（Eusociality）是最为复杂的社会组织形式之一，其特征为存在被称为社群（colonies）的合作与繁殖单元。社群内工蚁的利他行为可通过广义适合度（inclusive fitness）理论解释，即通过协助亲属获取间接适合度收益。社会性昆虫社群的成员彼此间的亲缘关系，理应较与其他同种个体的亲缘关系更为紧密。在诸多社会性昆虫类群中，单个社群可由多个社会联结但空间分离的巢群构成，该现象被称为多巢型（polydomy）。巢间通路等社会联结可促进合作与资源交换，我们据此预测：存在社会联结的巢群，其工蚁的巢间亲缘关系将高于无社会联结且无合作行为的巢群。我们以多巢型红褐林蚁（Formica lugubris）为研究对象，通过测定其社会联结强度、资源交换模式及巢间遗传亲缘关系，以验证两项假设：（1）存在社会联结但空间分离的巢群是否存在合作行为；（2）高巢间亲缘关系是否为该合作行为的潜在驱动因素。本研究结果显示，存在社会联结的巢群间存在工蚁与资源的移动现象，提示二者确实存在合作行为，而无社会联结的巢群则未观察到此类行为。然而，我们并未发现社会联结巢群与无联结巢群间的巢间遗传亲缘关系存在显著差异，两类巢群均表现出较高的亲缘关系。本研究结果表明，存在社会联结的邻近巢群呈现出社会与合作层面的分化，却未出现遗传层面的分化。我们据此推测，社会联结的丧失或会引发社群内部的生态分化，而邻近巢群间的遗传分化或仅会在后续逐步形成，其并非社群分离的成因，而是其结果。