Data from: Biological markets in cooperative breeders: quantifying outside options

A major aim in evolutionary biology is to understand altruistic help and reproductive partitioning in cooperative societies, where subordinate helpers forego reproduction to rear dominant breeders' offspring. Traditional models of cooperation in these societies typically make a key assumption: that the only alternative to staying and helping is solitary breeding, an often unfeasible task. Using large-scale field experiments on paper wasps (Polistes dominula), we show that individuals have high-quality alternative nesting options available that offer fitness payoffs just as high as their actual chosen options, far exceeding payoffs from solitary breeding. Furthermore, joiners could not easily be replaced if they were removed experimentally, suggesting that it may be costly for dominants to reject them. Our results have implications for expected payoff distributions for cooperating individuals, and suggest that biological market theory, which incorporates partner choice and competition for partners, is necessary to understand helping behaviour in societies like that of P. dominula. Traditional models are likely to overestimate the incentive to stay and help, and therefore the amount of help provided, and may underestimate the size of reproductive concession required to retain subordinates. These findings are relevant for a wide range of cooperative breeders where there is dispersal between social groups.进化生物学的核心目标之一，是解析合作社会中的利他助人行为与生殖分工（reproductive partitioning）——在此类社会中，从属帮手会放弃自身繁殖机会，以抚育优势繁殖个体的后代。此类合作社会的传统合作模型通常会做出一项关键假设：即选择留下并提供帮助的唯一替代方案是单独繁殖，而这往往是一项难以实现的任务。本研究通过针对造纸胡蜂（Polistes dominula）开展的大规模野外实验发现，个体可获得高质量的备选筑巢方案，其带来的适合度收益与个体实际选择的方案相当，且远高于单独繁殖所能获得的收益。此外，若通过实验移除加入群体的帮手，此类个体难以被轻易替代，这表明优势繁殖者拒绝这些帮手可能需要付出高昂代价。本研究结果对合作个体的预期收益分布具有启示意义，同时表明，若要解析如造纸胡蜂这类合作社会中的助人行为，纳入了伴侣选择与伴侣竞争要素的生物学市场理论（biological market theory）不可或缺。传统模型很可能高估了个体留下并提供帮助的动机，进而高估了实际提供的帮助总量，同时可能低估了留住从属帮手所需的生殖让步（reproductive concession）规模。上述研究结论对诸多存在社会群体间扩散现象的合作繁殖物种均具有参考价值。