Department of Neurobiology and Behavior, Cornell University, Ithaca, NY, USA.
Smithsonian Tropical Research Institute, Panama City, Panama.
J Chem Ecol. 2021 May;47(4-5):420-432. doi: 10.1007/s10886-021-01262-1. Epub 2021 Mar 8.
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.
蜂王信息素在多个真社会性昆虫谱系中独立进化，通过抑制工蜂卵巢发育来调节生殖冲突。尽管它们对生殖分工至关重要——这是真社会性的标志——但它们的进化起源仍然是个谜。在这里，我们分析了 Megalopta genalis 蜜蜂（拟熊蜂族，蜜蜂科）替代社会和生殖表型的表皮和 Dufour 腺化学物质，这些蜜蜂具有简单的社会性，是兼性表达的。与非生殖工蜂相比，生殖蜜蜂具有独特的整体腺体和表皮化学表型。在表皮上，信号传递的一个可能部位，生殖者富含某些烯烃、大多数线性烷烃，并富含所有甲基支链烷烃。在其他真社会性昆虫类群中，属于这些化合物类别的化学物质被认为是作为生殖信号。一些大环内酯，作为其他真社会性 Halictini 族（拟熊蜂族）中蜂王信息素的化合物，在生殖者中相对于工蜂也更为丰富。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——独自繁殖的个体（独居生殖者）和社会性女王——以突出后者可能是社会性重要调节者的特征。与独居生殖者相比，女王的表皮化学物质与工蜂的化学物质差异更大，并且特别富含甲基支链烷烃。确定我们鉴定的候选信号化合物的信息素功能和信息量将有助于阐明蜂王信息素的早期进化历史，信息素是昆虫社会性行为组织的核心化学信号。
