Data from: Pheromone-induced accuracy of nestmate recognition in carpenter ants: simultaneous decrease of Type I and Type II errors

The ecological and evolutionary success of social insects relies on their ability to efficiently discriminate between group members and aliens. Nestmate recognition occurs by phenotype matching, the comparison of the referent (colony) phenotype to the one of an encountered individual. Based on the level of dissimilarity between the two, the discriminator accepts or rejects the target. The tolerated degree of mismatch is predicted by the acceptance threshold model, which assumes adaptive threshold shifts depending on the costs of discrimination errors. Inherent in the model is that rejection (Type I) and acceptance (Type II) errors are reciprocally related: if one type decreases, the other increases. We studied whether alarm pheromones modulate the acceptance threshold. We exposed Camponotus aethiops ants to formic acid and subsequently measured aggression towards nestmates and non-nestmates. Formic acid induced both more non-nestmate rejection and more nestmate acceptance than a control treatment, thus uncovering an unexpected effect of an alarm pheromone on responses to nestmates. Nestmate discrimination accuracy was improved via a decrease of both types of errors, a result that cannot be explained by a shift in the acceptance threshold. We propose that formic acid increases the amount of information available to the ants, thus decreasing the perceived phenotypic overlap between nestmate and non-nestmate recognition cues. This mechanism for improved discrimination reveals a novel function of alarm pheromones in recognition processes and may have far-reaching implications in our understanding of the modus operandi of recognition systems in general.社会性昆虫（social insects）在生态与演化维度的成功，核心依赖于其高效区分巢友与异类的能力。巢友识别通过表型匹配（phenotype matching）实现：即参照巢群的表型特征，与遭遇个体的表型进行比对。识别者会依据二者的差异程度，决定接受或拒斥目标个体。可容忍的错配程度由接受阈值模型（acceptance threshold model）预测，该模型假定阈值会随识别错误的成本发生适应性偏移。该模型的内在逻辑在于：拒斥错误（一类错误，Type I）与接受错误（二类错误，Type II）呈负相关关系——若一类错误减少，另一类错误便会增加。本研究旨在探究告警信息素（alarm pheromones）是否会调控接受阈值。我们以亮毛弓背蚁（Camponotus aethiops）为实验材料，将其暴露于甲酸环境中，随后测定其对巢友与非巢友的攻击行为。相较于对照组，甲酸处理不仅提升了对非巢友的拒斥率，同时也增强了对巢友的接受度，由此揭示了告警信息素对巢友识别反应的意外调控效应。本研究中，两类识别错误均有所降低，从而提升了巢友识别的准确率，这一结果无法通过接受阈值的偏移来解释。我们提出，甲酸可提升蚂蚁可获取的信息总量，进而降低巢友与非巢友识别信号间的感知表型重叠度。这一优化识别的机制，揭示了告警信息素在识别过程中的全新功能，或可为我们全面理解各类识别系统的运作模式带来深远影响。