With one of the highest number of parasite, eusocial and pollinator species among all insect orders, Hymenoptera features a great diversity of specific lifestyles. At the population genetic level, such life-history strategies are expected to decrease effective population size and efficiency of purifying selection. In this study, we tested this hypothesis by estimating the relative rate of non-synonymous substitution in 169 species to investigate the variation in natural selection efficiency throughout the hymenopteran tree of life. We found no effect of parasitism or body size, but show that relaxed selection is associated with eusociality, suggesting that the division of reproductive labour decreases effective population size in ants, bees and wasps. Unexpectedly, the effect of eusociality is marginal compared to a striking and widespread relaxation of selection in both social and non social bees, which indicates that these keystone pollinator species generally feature low effective population sizes. This widespread pattern suggests specific constraints in pollinating bees potentially linked to limited resource and high parental investment. The particularly high load of deleterious mutations we report in the genome of these crucial ecosystem engineer species also raises new concerns about their ongoing population decline.

中文翻译：

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放宽选择纯化表明，正常社会膜翅目和孤立授粉蜂的有效种群数量低

膜翅目是所有昆虫纲中寄生虫，常社会和授粉媒介中数量最多的物种之一，具有多种多样的特定生活方式。在种群遗传水平上，预期这种生活史策略会减少有效种群数量和纯化选择的效率。在这项研究中，我们通过估计169种非同义替代的相对比率来研究整个假设，以调查整个膜翅类生物在自然选择效率方面的变化。我们没有发现寄生虫或体型的影响，但是表明放松的选择与善意相关，表明生殖分工会降低蚂蚁，蜜蜂和黄蜂的有效种群数量。不料，与社会性和非社会性蜂的选择显着而广泛的放宽相比，善意的影响微乎其微，这表明这些主要的传粉媒介物种通常具有较低的有效种群数量。这种普遍的模式表明，授粉蜜蜂的特殊限制可能与有限的资源和较高的父母投资有关。我们在这些关键的生态系统工程物种的基因组中报告的有害突变负荷特别高，这也引起了人们对其种群持续减少的新担忧。这种普遍的模式表明，授粉蜜蜂的特殊限制可能与有限的资源和较高的父母投资有关。我们在这些关键的生态系统工程物种的基因组中报告的有害突变负荷特别高，这也引起了人们对其种群持续减少的新担忧。这种普遍的模式表明，授粉蜜蜂的特定限制可能与资源有限和父母投资高有关。我们在这些关键的生态系统工程物种的基因组中报告的有害突变负荷特别高，这也引起了人们对其种群持续减少的新担忧。