Center for Population Biology, University of California , Davis, CA , USA.
Proc Biol Sci. 2019 Jul 10;286(1906):20190588. doi: 10.1098/rspb.2019.0588.
The evolution of eusociality and sterile worker castes represents a major transition in the history of life. Despite this, little is known about the mechanisms involved in the initial transition from solitary to social behaviour. It has been hypothesized that plasticity from ancestral solitary life cycles was coopted to create queen and worker castes in insect societies. Here, we tested this hypothesis by examining gene expression involved in the transition from solitary to social behaviour in the orchid bee Euglossa dilemma. To this end, we conducted observations that allowed us to classify bees into four distinct categories of solitary and social behaviour. Then, by sequencing brain and ovary transcriptomes from these behavioural phases, we identified gene expression changes overlapping with socially associated genes across multiple eusocial lineages. We find that genes involved in solitary E. dilemma ovarian plasticity overlap extensively with genes showing differential expression between fertile and sterile workers-or between queens and workers in other eusocial bees. We also find evidence that sociality in E. dilemma reflects gene expression patterns involved in solitary foraging and non-foraging nest care behaviours. Our results provide strong support for the hypothesis that eusociality emerges from plasticity found across solitary life cycles.
社会性和不育工蜂等级的进化代表了生命历史上的一个主要转折点。尽管如此，对于从独居到群居行为的最初转变所涉及的机制知之甚少。有人假设，从祖先独居生活史中获得的可塑性被用来在昆虫社会中创造蜂王和工蜂等级。在这里，我们通过检查兰花蜜蜂 Euglossa dilemma 中从独居到群居行为转变所涉及的基因表达来检验这一假设。为此，我们进行了观察，使我们能够将蜜蜂分为四个不同的独居和群居行为类别。然后，通过对这些行为阶段的大脑和卵巢转录组进行测序，我们确定了与多个真社会性谱系中与社会相关的基因重叠的基因表达变化。我们发现，涉及独居 Euglossa dilemma 卵巢可塑性的基因与在有生殖力和不育工蜂之间或在其他真社会性蜜蜂中蜂王和工蜂之间表现出差异表达的基因广泛重叠。我们还发现，E. dilemma 的社会性反映了涉及独居觅食和非觅食巢护理行为的基因表达模式。我们的研究结果为社会性从独居生活史中发现的可塑性产生的假设提供了有力支持。
