Queen pheromones evolved independently in multiple eusocial insect lineages, in which they mediate reproductive conflict by inhibiting worker ovarian development. Although fundamentally important for reproductive division of labor – the hallmark of eusociality – their evolutionary origins are enigmatic. Here, we analyze cuticular and Dufour’s gland chemistries across alternative social and reproductive phenotypes in Megalopta genalis bees (tribe Augochlorini, family Halictidae) that facultatively express simple eusociality. Reproductive bees have distinct overall glandular and cuticular chemical phenotypes compared with non-reproductive workers. On the cuticle, a likely site of signal transmission, reproductives are enriched for certain alkenes, most linear alkanes, and are heavily enriched for all methyl-branched alkanes. Chemicals belonging to these compound classes are known to function as fertility signals in other eusocial insect taxa. Some macrocyclic lactones, compounds that serve as queen pheromones in the other eusocial halictid tribe (Halictini), are also enriched among reproductives relative to workers. The intra-population facultative eusociality of M. genalis permits direct comparisons between individuals expressing alternative reproductive phenotypes – females that reproduce alone (solitary reproductives) and social queens – to highlight traits in the latter that may be important mediators of eusociality. Compared with solitary reproductives, the cuticular chemistries of queens are more strongly differentiated from those of workers, and furthermore are especially enriched for methyl-branched alkanes. Determining the pheromonal function(s) and information content of the candidate signaling compounds we identify will help illuminate the early evolutionary history of queen pheromones, chemical signals central to the organization of insect eusocial behavior.

女王信息素在多个真社会性昆虫谱系中独立进化，在这些谱系中，它们通过抑制工人卵巢发育来调解生殖冲突。尽管对生殖分工（真社会性的标志）至关重要，但它们的进化起源却是个谜。在这里，我们分析了Megalopta genalis 中不同社会和生殖表型的表皮和 Dufour 腺体化学兼性地表达简单的社会性的蜜蜂（部落 Augochlorini，家庭 Halictidae）。与非生殖蜜蜂相比，生殖蜜蜂具有不同的整体腺体和表皮化学表型。在角质层上，可能是信号传输的部位，再生部分富含某些烯烃，大多数直链烷烃，并且所有甲基支链烷烃都非常丰富。已知属于这些化合物类别的化学物质在其他真社会性昆虫分类群中起到生育信号的作用。一些大环内酯，在其他真社会 halictid 部落 (Halictini) 中作为女王信息素的化合物，在相对于工人的繁殖中也很丰富。M. genalis的种群内兼性社会性允许在表达替代生殖表型的个体之间进行直接比较 - 女性单独繁殖（单独繁殖）和社会女王 - 以突出后者可能是社会性的重要调解者的特征。与单独繁殖相比，蜂王的表皮化学成分与工蜂的表皮化学成分差异更大，而且甲基支链烷烃含量特别高。确定我们确定的候选信号化合物的信息素功能和信息内容将有助于阐明蜂王信息素的早期进化历史，这是昆虫社会行为组织的核心化学信号。