Conflict resolution and direct benefits in kin-selected conflicts in social groups

亲缘选择理论是解释生物社会行为进化的主要理论。该理论的基础是将自然选择理论应用于影响社会行为的基因，其中社会行为包括合作和冲突。它提出，个体对彼此的评价与他们的遗传亲缘成正比，因为亲缘关系衡量的是他们分享影响社会行为的基因的机会。由于亲缘选择的基本基础，以及解释动物社会性复杂性的需要，研究亲缘选择是进化生态学家的主要兴趣。事实证明，这个理论在解释某些社会现象方面非常成功，但在其他方面则不然。人们提出了这一理论失败的两个一般原因。首先，社会互动是由理论中尚未得到充分研究的方面来解决的，即，在社会冲突中，不同个体所拥有的相对权力，和/或冲突行为对社会群体的总体成本。第二种解释是，个人的社会行为是由直接利益（来自个人再生产的收益）驱动的，而不是亲属选择的利益。我们建议用大黄蜂Bombus terrestris作为我们的研究生物来测试这两个想法。在群居的膜翅目昆虫（蚂蚁、蜜蜂和黄蜂）中，亲缘选择预测，蜂王或工蜂（如果能繁殖，只生儿子）应该垄断成年雄性后代的生产，这取决于群体的亲缘关系结构。但实际的工人再生产水平往往远低于预期。这就是B. terrestris的情况。在这个物种中，理论预测工蜂应该产生大多数成年雄性，但我们的数据显示，实际上它们只产生了5%。我们提出检验两个假设，在雄性亲本数据和亲缘选择理论的预测之间缺乏拟合。这两种假设分别源于解决冲突（通过权力的不平等分配）和直接利益的理念。它们是：(1)大多数工蜂产下的卵会被蚁后或其他工蜂选择性地摧毁，这在很大程度上取决于它们对雄性后代的控制力；(2)正如亲缘选择理论所提出的那样，工蜂的繁殖不是由工蜂与雌蜂的亲缘关系决定的，而是工蜂种内社会寄生能力的副产品。这些假设来自两组观察。首先，在B. terrestris中，工蜂产下的卵经常被蚁后或其他工蜂吃掉，尽管这种情况的程度从未被量化过。第二个是我们最近的发现，B. terrestris工蜂进入自己物种的其他殖民地，然后作为生殖“漂流者”（种内社会寄生虫）生产儿子。我们将通过观察、实验和遗传亲代分析（基于微卫星标记）来检验假设1，以确定地圆蝽中工蜂产卵的主要消费者是蚁后、繁殖工蜂还是整个工蜂。我们将通过使用相同的技术来检验假设2，以确定拥有最多常驻工蚁繁殖的殖民地是否输出最多繁殖的漂流工蚁，以及/或者繁殖漂流工蚁是否在与常驻工蚁的优势争夺战中处于劣势。我们还将测量野外种群中繁殖漂移工蚁的频率以及巢聚集对漂移行为的影响。我们计划的工作是新颖的，因为它解决了新的现象和未解决的研究问题。它的影响将是广泛的，因为研究的基本性质，对社会进化的广泛兴趣，以及结果可能会导致对长期存在的概念的重新评估。它将大大推进我们对社会行为进化生态学的理解。

Kin selection theory is the leading theory for explaining the evolution of social behaviour in organisms. The theory is based on the application of natural selection theory to the genes that influence social behaviour, where social behaviour includes both cooperation and conflict. It proposes that individuals value one another in proportion to their genetic relatedness, since relatedness measures the chance they share the genes influencing the social behaviour. Because of its fundamental basis, and the need to explain the complexity of animal sociality, investigating kin selection is of major interest to evolutionary ecologists. The theory has proved very successful in explaining social phenomena in some respects, but not in others. Two general reasons for the failures of the theory have been proposed. The first is that social interactions are resolved by as-yet poorly-investigated aspects of the theory, namely, in social conflicts, the relative power held by different sets of individuals, and/or the overall costs to the social group of conflict behaviour. The second explanation is that individuals' social behaviour is driven by direct benefits (gains from personal reproduction), not kin-selected benefits. We propose to test both these ideas using the bumble bee Bombus terrestris as our study organism. In the social Hymenoptera (ants, bees and wasps), kin selection predicts that either queens or workers (which, if reproductive, produce only sons) should monopolise the production of adult male offspring, depending on the relatedness structure of the colony. But the actual level of worker reproduction is often far lower than that predicted. This is the case in B. terrestris. In this species, the theory predicts that workers should produce most of the adult males, but our data show that in fact they produce only c. 5%. We propose to test two hypotheses for the lack of fit between male parentage data and predictions of kin selection theory in B. terrestris. The hypotheses stem, respectively, from the ideas of conflict resolution (through the unequal distribution of power) and direct benefits. They are: (1) most worker-laid eggs are selectively destroyed by the queen or by other workers, with which power over male parentage largely lies; and (2) worker reproduction is not determined by the relatedness of workers to nestmates, as kin selection theory proposes, but is instead a by-product of workers' capacity for intraspecific social parasitism. These hypotheses arise from two sets of observations. The first is that worker-laid eggs in B. terrestris are frequently eaten by the queen or other workers, although the extent of this has never been quantified. The second is our recent discovery that B. terrestris workers enter other colonies of their own species in which they then produce sons as reproductive 'drifters' (intraspecific social parasites). We will test Hypothesis 1 by using observations, experimentation and genetic parentage analyses (based on microsatellite markers) to determine whether the major consumers of worker-laid eggs in B. terrestris are the queen, reproductive workers, or workers as a whole. We will test Hypothesis 2 by using the same techniques to determine whether colonies with the most reproduction by resident workers are those exporting the most reproductive drifter workers, and/or whether reproductive drifters are losers in dominance battles with resident workers. We will also measure the frequency of reproductive drifter workers in field colonies and effects of nest aggregation on drifting behaviour. Our planned work is novel because it addresses new phenomena and unanswered research questions. Its impact will be broad because of the fundamental nature of the research, widespread interest in social evolution, and the possibility that the results will cause a reassessment of long-standing concepts. It should advance considerably our understanding of the evolutionary ecology of social behaviour.