Data from: Reproductive conflict in bumblebees and the evolution of worker policing

Worker policing (mutual repression of reproduction) in the eusocial Hymenoptera represents a leading example of how coercion can facilitate cooperation. The occurrence of worker policing in “primitively” eusocial species with low mating frequencies, which lack relatedness differences conducive to policing, suggests that separate factors may underlie the origin and maintenance of worker policing. We tested this hypothesis by investigating conflict over male parentage in the primitively eusocial, monandrous bumblebee, Bombus terrestris. Using observations, experiments, and microsatellite genotyping, we found that: (a) worker- but not queen-laid male eggs are nearly all eaten (by queens, reproductive, and nonreproductive workers) soon after being laid, so accounting for low observed frequencies of larval and adult worker-produced males; (b) queen- and worker-laid male eggs have equal viabilities; (c) workers discriminate between queen- and worker-laid eggs using cues on eggs and egg cells that almost certainly originate from queens. The cooccurrence in B. terrestris of these three key elements of “classical” worker policing as found in the highly eusocial, polyandrous honeybees provides novel support for the hypothesis that worker policing can originate in the absence of relatedness differences maintaining it. Worker policing in B. terrestris almost certainly arose via reproductive competition among workers, that is, as "selfish" policing.

工蜂警戒(Worker policing，即繁殖相互抑制)在真社会性膜翅目昆虫中是胁迫促进合作的典型范例。在缺乏利于工蜂警戒的亲缘关系差异、且交配频率较低的"原始"真社会性物种中发现工蜂警戒现象，这表明工蜂警戒的起源与维持或许存在其他独立作用因子。本研究以原始真社会性、单雄交配的地熊蜂(Bombus terrestris)为研究对象，通过探究其雄性亲本冲突对该假说进行了验证。本研究采用观察法、实验法与微卫星基因分型技术开展研究，得到如下结果：(a) 工蜂所产的雄性卵几乎会在产下后立即被蜂王、有繁殖能力的工蜂以及无繁殖能力的工蜂取食清除，而蜂王所产的雄性卵则不会遭遇此情况，这解释了野外观测到的工蜂繁殖的雄性幼虫与成虫发生率极低的现象；(b) 蜂王与工蜂所产的雄性卵存活能力无显著差异；(c) 工蜂可通过卵表面及卵室上的识别线索区分蜂王与工蜂所产的卵，且此类线索几乎可确定均来自蜂王。在多雄交配的高级真社会性蜜蜂中，已发现"经典"工蜂警戒的三大核心特征；而地熊蜂(Bombus terrestris)中这三大特征的共同出现，为"工蜂警戒可在缺乏维持其存在的亲缘关系差异的情况下起源"这一假说提供了全新的实验支持。地熊蜂中的工蜂警戒几乎可确定起源于工蜂间的繁殖竞争，即属于"自私型"警戒行为。