Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland.
Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
Sci Rep. 2021 Oct 1;11(1):19559. doi: 10.1038/s41598-021-98098-2.
Cuticular hydrocarbons (CHCs) have important communicative functions for ants, which use CHC profiles to recognize mutualistic aphid partners. Aphid endosymbionts can influence the quality of their hosts as ant mutualists, via effects on honeydew composition, and might also affect CHC profiles, suggesting that ants could potentially use CHC cues to discriminate among aphid lines harbouring different endosymbionts. We explored how several strains of Hamiltonella defensa and Regiella insecticola influence the CHC profiles of host aphids (Aphis fabae) and the ability of aphid-tending ants (Lasius niger) to distinguish the profiles of aphids hosting different endosymbionts. We found significant compositional differences between the CHCs of aphids with different infections. Some endosymbionts changed the proportions of odd-chain linear alkanes, while others changed primarily methyl-branched compounds, which may be particularly important for communication. Behavioural assays, in which we trained ants to associate CHC profiles of endosymbiont infected or uninfected aphids with food rewards, revealed that ants readily learned to distinguish differences in aphid CHC profiles associated with variation in endosymbiont strains. While previous work has documented endosymbiont effects on aphid interactions with antagonists, the current findings support the hypothesis that endosymbionts also alter traits that influence communicative interactions with ant mutualists.
表皮碳氢化合物（CHC）对蚂蚁具有重要的交流功能，蚂蚁利用 CHC 图谱来识别互利共生的蚜虫伙伴。蚜虫内共生体可以通过影响蜜露的组成来影响其作为蚂蚁互利共生者的质量，并且还可能影响 CHC 图谱，这表明蚂蚁可能可以利用 CHC 线索来区分携带不同内共生体的蚜虫谱系。我们探讨了几种防御 Hamiltonella 和 Regiella insecticola 菌株如何影响宿主蚜虫（Aphis fabae）的 CHC 图谱，以及蚜虫饲养蚂蚁（Lasius niger）区分不同内共生体宿主的 CHC 图谱的能力。我们发现不同感染的蚜虫之间的 CHC 存在显著的组成差异。一些内共生体改变了奇数链线性烷烃的比例，而另一些内共生体主要改变了支链甲基化合物，这对内共生体的交流可能尤为重要。在行为测定中，我们训练蚂蚁将内共生体感染或未感染的蚜虫的 CHC 图谱与食物奖励联系起来，结果表明蚂蚁很容易学会区分与内共生体菌株变化相关的蚜虫 CHC 图谱的差异。虽然之前的工作已经记录了内共生体对蚜虫与拮抗剂相互作用的影响，但目前的发现支持了这样一种假设，即内共生体也会改变影响与蚂蚁互利共生者交流的特征。
