Lifetime reproductive success and longevity of workers in a social insect

社会行为的进化和衰老的进化都是进化生态学的主要研究领域。社会行为的进化涉及动物社会如何产生和维持，如真社会性昆虫（蚂蚁，蜜蜂，黄蜂和白蚁）。衰老的演变涉及影响生物体寿命和其一生中繁殖模式的因素。最近，研究人员意识到这些区域是相互联系的，传统的衰老模式可能会受到社会性的严重影响。一个关键的例子涉及终身生殖成功（一个人一生中拥有的后代数量）和寿命之间的关系。衰老的标准进化理论预测，外部死亡的来源（导致外部环境死亡的因素，如捕食者、事故等）选择更早的繁殖，而这反过来又由更早的死亡支付。这预示着终生生殖成功与寿命之间存在负相关关系，即生育更多后代的个体寿命较短。但是，在包含繁殖和帮助个体的真社会中，研究人员预测繁殖者应该表现出终生繁殖成功与长寿之间的正相关关系，即生育更多后代的个体寿命更长。这是因为在真社会社会中，繁殖者留在巢中可以避免外来死亡。首席研究员最近的研究证实了这一预测，首次证明了一种真社会性昆虫熊蜂（Bombus terrestris）的蜂王一生的生殖成功与寿命之间的正相关关系。与许多其他真社会性昆虫一样，土生蚁的工蚁都是蚁后的女儿，它们可以生育一些自己的后代。由于蜜蜂的性别决定系统，工蜂的后代总是雄性。像蚁后一样，如果它们倾向于留在巢中，生殖工人将免受外部死亡的影响，但如果它们经常离开巢去觅食，就不会受到外部死亡的影响。这使得假设的影响，外部死亡率被隔离，因为它导致的预测，生殖工人将表现出积极的关系，终身生殖成功和长寿，如果他们倾向于留在巢和负相关的关系，如果他们倾向于离开巢觅食。这个项目的目的是用B来检验这个假设。terrestris作为研究生物，该项目是可行的，因为B.土蜂是一年生的真群居昆虫，即在一个季节完成其群体周期的昆虫，因此，在这种昆虫中，蚁后和工蜂在殖民地中最多生活几个月。B。土生菌菌落也是市售的，并且易于在实验室中保存和观察。所有母蚁后的一生繁殖成功率和寿命以及它们的繁殖工蚁女儿的样本将在一组工蚁被单独标记的殖民地中确定。出生和死亡日期，在巢中度过的时间和一生的繁殖成功将在所有个体中进行测量，一生的繁殖成功将通过产卵（从巢的拍摄中测量）和使用遗传标记对雄性进行亲子分析来测量。这项研究是新颖的和根本的，因为它将在社会演变和老龄化演变的重要领域的界面上测试新的概念。因此，这项工作将大大推进我们对社会性和老龄化的基本理解。

The evolution of social behaviour and the evolution of ageing both form major areas of study in evolutionary ecology. The evolution of social behaviour concerns how animal societies such as those of the eusocial insects (ants, bees, wasps and termites) arise and are maintained. The evolution of ageing concerns the factors that affect the longevity of organisms and the pattern of reproduction over their lifetimes. Recently, researchers have realised that these areas are connected, and that orthodox patterns of ageing can be heavily affected by sociality. A key example involves the relationship between lifetime reproductive success (the number of offspring an individual has over its lifetime) and longevity. The standard evolutionary theory of ageing predicts that sources of extrinsic mortality (factors leading to death in the external environment, such as predators, accidents, and so on) select for earlier reproduction, which in turn is paid for by earlier death. This predicts a negative relationship between lifetime reproductive success and longevity, i.e. that individuals producing more offspring have shorter lives. But, in eusocial societies, which contain both breeding and helping individuals, researchers have predicted that the breeders should exhibit a positive relationship between lifetime reproductive success and longevity, i.e. that individuals producing more offspring have longer lives. This is because breeders in eusocial societies are protected against extrinsic mortality by remaining in the nest. The principal investigator's research recently confirmed this prediction by demonstrating for the first time a positive relationship between lifetime reproductive success and longevity in queens of a eusocial insect, the bumble bee Bombus terrestris.In B. terrestris, as in many other eusocial insects, the workers, which are all daughters of the queen, can produce some offspring of their own. Because of the sex determination system in bees, workers' offspring are always males. Reproductive workers will, like queens, be protected from extrinsic mortality if they tend to remain in the nest, but not if they routinely leave the nest to forage. This allows the hypothesized effect of extrinsic mortality to be isolated, because it leads to the prediction that reproductive workers will exhibit a positive relationship between lifetime reproductive success and longevity if they tend to remain in the nest and a negative relationship if they tend to leave the nest to forage. The aim of this project is to test this hypothesis using B. terrestris as the study organism.The project is feasible because B. terrestris is an annual eusocial insect, i.e. one completing its colony cycle in a single season and hence one in which queens and workers live in the colony for at most a few months. B. terrestris colonies are also commercially available and are easy to keep and observe in the laboratory. The lifetime reproductive success and longevity of all mother queens and a sample of their reproductive worker daughters will be determined in a set of colonies whose workers have been individually marked. Birth and death dates, time spent in the nest and lifetime reproductive success will be measured across all individuals, with lifetime reproductive success being measured both as egg-production (measured from filming of nests) and from parentage analyses of males using genetic markers. This research is novel and fundamental because it will test new concepts at the interface of the important areas of social evolution and the evolution of ageing. For this reason, the work will substantially advance our basic understanding of both sociality and ageing in general.