The effect of forager loss on honeybee workers temporal polyethism and social network structure

The western honeybee Apis mellifera is perhaps the best-known example of an advanced eusocial species displaying temporal polyethism, a process in which workers perform different tasks in the colony as they age. Previous studies demonstrated that this temporal division of labour is not only regulated by the age of the bees but also by the proportion of workers performing the required tasks in the colony. As we progress through the Anthropocene, the Intergovernmental Panel on Climate Change predicted that a significant increase in both the frequency and intensity of severe weather events can be expected in the coming decades. Here, we performed a controlled interrupted time series experiment with the objective of quantifying the possible effects that these weather events might have in the honeybee colony dynamics. By simulating a significant loss of foragers in the colony, we observed that honeybee workers quickly replaced the missing foragers by accelerating their transition to a subsequent task and, in some cases, completely skipped several of the natural task transitions with respect to their age. In addition, we analysed how the colony social network structure is affected by the sudden loss of foragers. Indeed, our data show that honeybee colonies increased their network cohesion with workers having a higher number of interactions as well as becoming more closely connected to one another soon after the disturbance. Overall, our data shows that even when faced with a substantial perturbation, honeybees can respond swiftly in order to maintain colony homeostasis and likely increase their resilience against future perturbations.

西方蜜蜂（Apis mellifera）或许是最为人熟知的高级真社会性物种范例，这类物种展现出时序劳动分工（temporal polyethism）——即工蜂会随着自身年龄增长，在蜂群中承担不同的劳作任务。既往研究表明，这种时序劳动分工不仅受蜜蜂自身年龄调控，同时也与蜂群内执行特定任务的工蜂占比息息相关。随着人类世（Anthropocene）的推进，政府间气候变化专门委员会（Intergovernmental Panel on Climate Change，IPCC）曾预测，未来数十年内极端天气事件的发生频率与强度都将显著提升。本研究开展了一项控制变量间断时间序列实验，旨在量化此类极端天气事件可能对蜂群动态产生的潜在影响。通过模拟蜂群中觅食蜂的大规模损失，我们观察到工蜂会通过加速向后续任务阶段的转变，快速填补缺失的觅食蜂缺口；在部分情境下，工蜂甚至会跳过与其年龄对应的若干自然任务过渡环节。此外，我们还分析了觅食蜂突然损失对蜂群社交网络结构的影响。研究数据证实，扰动发生后不久，蜂群的网络凝聚力有所提升：工蜂间的互动频次更高，群体内部的连接也更为紧密。总体而言，本研究数据表明，即便遭遇显著扰动，西方蜜蜂仍能迅速做出响应以维持蜂群内稳态（homeostasis），并大概率提升其抵御未来扰动的恢复能力。