In eusocial insects, chemical communication is crucial for mediating many aspects of social activities, especially the regulation of reproduction. Though queen signals are known to decrease ovarian activation of workers in highly eusocial species, little is known about their evolution. In contrast, some primitively eusocial species are thought to control worker reproduction through physical aggression by the queen rather than via pheromones, suggesting the evolutionary establishment of chemical signals with more derived sociality. However, studies supporting this hypothesis are largely missing. Socially polymorphic halictid bees, such as Halictus rubicundus, with social and solitary populations in both Europe and North America, offer excellent opportunities to illuminate the evolution of caste-specific signals. Here we compared the chemical profiles of social and solitary populations from both continents and tested whether (i) population or social level affect chemical dissimilarity and whether (ii) caste-specific patterns reflect a conserved queen signal. Our results demonstrate unique odor profiles of European and North American populations, mainly due to different isomers of n-alkenes and macrocyclic lactones; chemical differences may be indicative of phylogeographic drift in odor profiles. We also found common compounds overproduced in queens compared to workers in both populations, indicating a potential conserved queen signal. However, North American populations have a lower caste-specific chemical dissimilarity than European populations which raises the question if both use different mechanisms of regulating reproductive division of labor. Therefore, our study gives new insights into the evolution of eusocial behavior and the role of chemical communication in the inhibition of reproduction.

在真社会性昆虫中，化学通讯对于调节社会活动的许多方面，尤其是繁殖的调节至关重要。尽管众所周知，蚁后信号会降低高度社会性物种中工蚁的卵巢激活，但人们对它们的进化知之甚少。相比之下，一些原始社会性物种被认为是通过蜂王的身体攻击而不是通过信息素来控制工蚁的繁殖，这表明化学信号的进化建立具有更衍生的社会性。然而，支持这一假设的研究基本上缺失。具有社会多态性的 Halictid 蜜蜂，例如Halictus rubicundus ，在欧洲和北美都有群居和独居种群，为阐明种姓特定信号的演变提供了绝佳的机会。在这里，我们比较了来自两个大陆的社会和孤独人口的化学特征，并测试了（i）人口或社会水平是否影响化学差异以及（ii）种姓特定模式是否反映了保守的女王信号。我们的研究结果表明，欧洲和北美人群具有独特的气味特征，这主要是由于正烯烃和大环内酯的不同异构体所致；化学差异可能表明气味谱中的系统发育地理漂移。我们还发现，与两个种群中的工蚁相比，蚁后体内的常见化合物过量产生，这表明蚁后信号存在潜在的保守性。然而，北美人口的种姓特异性化学差异低于欧洲人口，这就提出了一个问题：两者是否使用不同的调节生殖分工的机制。 因此，我们的研究为社会行为的演变以及化学通讯在抑制繁殖中的作用提供了新的见解。