Am Nat. 2019 Feb;193(2):267-278. doi: 10.1086/701123. Epub 2018 Dec 13.
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 toward nestmates and nonnestmates. Formic acid induced both more nonnestmate 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 in 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 nonnestmate 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.
社会性昆虫的生态和进化成功依赖于它们能够有效地辨别群体成员和外来者的能力。巢内识别是通过表型匹配来实现的，即将参考（群体）表型与遇到的个体的表型进行比较。根据两者之间的相似度差异，判别器接受或拒绝目标。接受阈值模型预测了可容忍的不匹配程度，该模型假设适应性阈值会根据歧视错误的成本而发生变化。该模型的内在假设是，拒绝（I 型）和接受（II 型）错误是相互关联的：如果一种错误减少，另一种错误就会增加。我们研究了警报信息素是否会调节接受阈值。我们让 Camponotus aethiops 蚂蚁接触甲酸，然后测量它们对巢内和巢外蚂蚁的攻击性。与对照处理相比，甲酸诱导了更多的非巢内蚂蚁的排斥和更多的巢内蚂蚁的接受，从而揭示了一种警报信息素对巢内蚂蚁反应的意外影响。通过减少两种类型的错误，巢内蚂蚁的辨别准确性得到了提高，这一结果不能用接受阈值的变化来解释。我们提出，甲酸增加了蚂蚁可用的信息量，从而减少了巢内和巢外蚂蚁识别线索之间的感知表型重叠。这种提高辨别能力的机制揭示了警报信息素在识别过程中的新功能，可能对我们理解一般识别系统的运作方式具有深远的意义。
