Data from: Market forces influence helping behaviour in cooperatively breeding paper wasps

Biological market theory is potentially useful for understanding helping behaviour in animal societies. It predicts that competition for trading partners will affect the value of commodities exchanged. It has gained empirical support in cooperative breeders, where subordinates help dominant breeders in exchange for group membership, but so far without considering one crucial aspect: outside options. We find support for the existence of a biological market in paper wasps, Polistes dominula. We first show that females have a choice of cooperative partners. Second, by manipulating entire subpopulations in the field, we increased the supply of outside options for subordinates, freeing up suitable nesting spots and providing additional nesting partners. We predicted that by intensifying competition for help, our manipulation would force dominants to accept a lower price for group membership. As expected, subordinates reduced their foraging effort following our treatments. We conclude that to accurately predict the amount of help provided, social units cannot be viewed in isolation as has traditionally been done: the surrounding market must also be considered.

生物学市场理论（Biological Market Theory）有助于解析动物社会中的互助行为。该理论预测，对交易伙伴的竞争会影响交换资源的价值。该理论已在合作繁育类群（cooperative breeders）中获得实证支持：从属个体通过帮助优势繁育个体以换取群体成员资格，但迄今为止的相关研究均未考虑一个关键维度——外部选择。我们在纸巢胡蜂（Polistes dominula）中找到了支持生物学市场理论存在的证据。首先，我们证实雌性个体拥有选择合作伙伴的权利。其次，我们通过野外操控完整亚种群的方式，提升了从属个体可获得的外部选择供给，释放了适宜的筑巢位点并提供了额外的筑巢伙伴。我们预测，通过强化对互助行为的竞争，本实验的操控处理将迫使优势个体接受更低的群体成员资格准入代价。正如预期，经实验处理后，从属个体的觅食投入显著降低。我们的研究结论表明：若要精准预测个体提供的互助程度，不能如传统研究那般将社会单元孤立看待，还需将其所处的周边市场环境纳入考量范畴。