Abstract

Plasticity is a key trait when an individual’s role in the social environment, and hence its optimum phenotype, fluctuates unpredictably. Plasticity is especially important in primitively eusocial insects where small colony sizes and little morphological caste differentiation mean that individuals may find themselves switching from non-reproductive to reproductive roles. To understand the scope of this plasticity, workers of the primitively eusocial sweat bee Lasioglossum malachurum were experimentally promoted to the reproductive role (worker-queens) and their performance compared with foundress-queens. We focussed on how their developmental trajectory as workers influenced three key traits: group productivity, monopolisation of reproduction, and social control of foraging nest-mates. No significant difference was found between the number of offspring produced by worker-queens and foundress-queens. Genotyping of larvae showed that worker-queens monopolised reproduction in their nests to the same extent as foundress queens. However, non-reproductives foraged less and produced a smaller total offspring biomass when the reproductive was a promoted worker: offspring of worker-queens were all males, which are the cheaper sex to produce. Greater investment in each offspring as the number of foragers increased suggests a limit to both worker-queen and foundress-queen offspring production when a greater quantity of pollen arrives at the nest. The data presented here suggest a remarkable level of plasticity and represent one of the first quantitative studies of worker reproductive plasticity in a non-model primitively eusocial species.

Significance statement

The ability of workers to take on a reproductive role and produce offspring is expected to relate strongly to the size of their colony. Workers in species with smaller colony sizes should have greater reproductive potential to insure against the death of the queen. We quantified the reproductive plasticity of workers in small colonies of sweat bees by removing the queen and allowing the workers to control the reproductive output of the nest. A single worker then took on the reproductive role and hence prevented her fellow workers from producing offspring of their own. These worker-queens produced as many offspring as control queens, demonstrating remarkable worker plasticity in a primitively eusocial species.

中文翻译：

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姐妹们为自己做这件事：原始社会蜜蜂工人的广泛生殖可塑性

摘要

当个人在社会环境中的角色以及因此其最佳表型发生不可预测的波动时，可塑性是一个关键特征。可塑性在原始群居昆虫中尤为重要，因为小群落大小和形态种姓分化很少，这意味着个体可能会发现自己从非生殖角色转变为生殖角色。为了了解这种可塑性的范围，原始社会性汗蜂Lasioglossum malachurum的工人被实验提升为生殖角色（工人女王）和他们与创始人女王相比的表现。我们专注于他们作为工人的发展轨迹如何影响三个关键特征：群体生产力、繁殖垄断和觅食巢穴的社会控制。工人女王和创始人女王产生的后代数量没有显着差异。幼虫的基因分型表明，工蜂王在巢穴中垄断繁殖的程度与母蜂王后相同。然而，当生殖是被提升的工人时，非生殖性的觅食较少并且产生的后代总生物量较少：工人女王的后代都是男性，这是生产成本较低的性别。随着觅食者数量的增加，对每个后代的更大投资表明，当更多的花粉到达巢穴时，工蜂王和创始人王后的后代产量都会受到限制。这里提供的数据表明了显着的可塑性水平，并代表了非模型原始社会物种中工人生殖可塑性的首批定量研究之一。

意义陈述

预计工人承担生殖角色和生产后代的能力与其群体的规模密切相关。群体规模较小的物种中的工人应该具有更大的繁殖潜力，以确保不会死亡。我们通过移除蜂王并允许工蜂控制巢穴的繁殖输出来量化小群汗蜂中工蜂的繁殖可塑性。然后一个工人承担了生殖角色，因此阻止了她的同事生产自己的后代。这些工蜂王产生的后代与控制蜂王一样多，在一个原始的群居物种中表现出非凡的工蜂可塑性。