Similarities in recognition cues lead to the infiltration of non-nestmates in an ant species

Abstract Chemical cues are among the most important information sharing mechanisms in insect societies, in which cuticular hydrocarbons play a central role – e.g. from nestmate recognition to queen signaling. The nestmate recognition mechanism usually prevents intruders from taking advantage of the resources stored in the nest. However, nestmate recognition is not unconditionally effective and foreign individuals can sometimes infiltrate unrelated nests and take advantage of the colony resources. In this study we investigated the role of overall colony odor profiles on the ability of conspecific workers drifting into unrelated colonies. We hypothesized that drifters would have higher chances of success by infiltrating colonies with the odor profiles most similar to their own nest, avoiding being detected as non-nestmates. By performing a drifting bioassay, we found that workers of the ant Formica fusca infiltrated unrelated conspecific colonies at a rate of 2.4 %, significantly infiltrating colonies displaying CHC profiles most similar to their natal nests. Notably, methyl branched hydrocarbons seem to play a role as recognition cues in this species. In addition, we show that environmental rather than genetic factors are responsible for most contributions on the CHC phenotype, presenting ca. of 50 % and 27.5 % of explained variation respectively, and playing a major role on how worker ants detect and prevent the infiltration of non-nestmates in the colony. Hence, relying on cuticular hydrocarbons similarities could be a profitably evolutionary strategy by which workers can identify conspecific colonies, evade detection by guards and avoid competition with genetic relatives.摘要 化学信号是昆虫社会中最重要的信息交流机制之一，表皮碳氢化合物（cuticular hydrocarbons, CHC）在其中发挥核心作用——其功能涵盖巢友识别、蚁后信号传导等多个场景。巢友识别机制通常可阻止入侵者利用巢穴内储存的资源，但该机制并非绝对有效，外来个体有时可渗透至无关巢穴并获取该群体的资源。本研究探究了整体群体气味谱对同种工蚁漂移进入无关群体的能力的影响。我们提出假说：漂移个体若渗透进气味谱与自身原巢最为相似的群体，将拥有更高的成功概率，从而避免被识别为非巢友。通过开展漂移生物测定实验，我们发现丝光褐林蚁（Formica fusca）的工蚁以2.4%的比率渗透至无关同种群体，且显著更倾向于渗透表皮碳氢化合物谱与自身原巢相似度最高的群体。值得注意的是，甲基支链碳氢化合物似乎在该物种的识别信号中发挥作用。此外，我们证实，相较于遗传因素，环境因素对表皮碳氢化合物表型的贡献更大，二者分别可解释约50%与27.5%的表型变异，并在工蚁识别并阻止非巢友渗透巢穴的过程中扮演核心角色。因此，依托表皮碳氢化合物的相似性或许是一种具备进化优势的策略，工蚁可借此识别同种群体、躲避守卫的检测，并避免与遗传亲属产生竞争。