In eusocial Hymenoptera, queens and their helper offspring should favour different sex investment ratios. Queens should prefer a 1:1 investment ratio, as they are equally related to offspring of both sexes (r = 0.5). In contrast, helpers should favour an investment ratio of 3:1 towards the production of female brood. This conflict arises because helpers are more closely related to full sisters (r = 0.75) than brothers (r = 0.25). However, helpers should invest relatively more in male brood if relatedness asymmetry within their colony is reduced. This can occur due to queen replacement after colony orphaning, multiple paternity and the presence of unrelated alien helpers. We analysed an unprecedentedly large number of colonies (n = 109) from a UK population of Lasioglossum malachurum, an obligate eusocial sweat bee, to tease apart the effects of these factors on colony-level investment ratios. We found that multiple paternity, unrelated alien helpers and colony orphaning were all common. Queen-right colonies invested relatively more in females than did orphaned colonies, producing a split sex ratio. However, investment ratios did not change due to multiple paternity or the presence of alien helpers, reducing inclusive fitness pay-offs for helpers. Queen control may also have been important: helpers rarely laid male eggs, and investment in female brood was lower when queens were large relative to their helpers. Genetic relatedness between helpers and the brood that they rear was 0.43 in one year and 0.37 in another year, suggesting that ecological benefits, as well as relatedness benefits, are necessary for the maintenance of helping behaviour. How helping behaviour is maintained in eusocial species is a key topic in evolutionary biology. Colony-level sex investment ratio changes in response to relatedness asymmetries can dramatically influence inclusive fitness benefits for helpers in eusocial Hymenoptera. The extent to which helpers in primitively eusocial colonies can respond adaptively to different sources of variation in relatedness asymmetry is unclear. Using data from 109 colonies of the sweat bee Lasioglossum malachurum, we found that queen loss, but not multiple paternity or the presence of alien helpers, was correlated with colony sex investment ratios. Moreover, we quantified average helper-brood genetic relatedness to test whether it is higher than that predicted under solitary reproduction (r = 0.5). Values equal to and below r = 0.5 suggest that relatedness benefits alone cannot explain the maintenance of helping behaviour. Ecological benefits of group living and/or coercion must also contribute.

中文翻译：

---

原始社会性汗蜂的性别比例和遗传相关性

在真社会性膜翅目中，蜂后及其辅助后代应该偏好不同的性别投资比例。皇后区应该更喜欢 1:1 的投资比例，因为它们与两性后代的相关性相同 (r = 0.5)。相比之下，帮手应该赞成对雌性育雏的投资比例为 3:1。之所以出现这种冲突，是因为帮手与全姐妹 (r = 0.75) 的关系比与兄弟 (r = 0.25) 的关系更密切。但是，如果群体内的亲缘关系不对称减少，则帮助者应该在雄性育雏上投入更多。这可能是由于殖民地孤儿后的女王更替、多重父系和无关的外星帮手的存在而发生的。我们分析了来自英国 Lasioglossum malachurum 种群的前所未有的大量菌落（n = 109），这是一种专性的真社会性汗蜂，梳理这些因素对殖民地水平投资比率的影响。我们发现多重父子关系、无关的外星帮手和殖民地孤儿都很常见。与孤儿殖民地相比，女王右翼殖民地对雌性的投资相对更多，从而产生了分裂的性别比例。然而，投资比率并没有因为多重父子关系或外来帮手的存在而改变，从而降低了帮手的包容性健身回报。蜂后控制也可能很重要：助手很少产雄性卵，当蜂后相对于它们的助手较大时，对雌性育雏的投资较低。帮助者和他们饲养的后代之间的遗传相关性在一年中为 0.43，在另一年中为 0.37，这表明生态效益和亲缘关系效益对于维持帮助行为是必要的。如何在真社会物种中维持助人行为是进化生物学的一个关键课题。响应亲缘关系不对称的群体级性投资比率变化可以显着影响真社会性膜翅目助手的包容性健康益处。原始真社会群体中的助手在多大程度上可以对相关性不对称的不同变异来源做出适应性反应，目前尚不清楚。使用来自汗蜂 Lasioglossum malachurum 的 109 个群落的数据，我们发现蜂王的损失与群落性别投资比率相关，但与多个亲子关系或外星助手的存在无关。此外，我们量化了平均辅助 - 育雏遗传相关性，以测试它是否高于单独繁殖下的预测值 (r = 0.5)。等于和小于 r = 0 的值。5 表明亲缘关系的好处不能解释帮助行为的维持。集体生活和/或胁迫的生态效益也必须有所贡献。