Data from: Evolution of ageing, costs of reproduction and the fecundity-longevity trade-off in eusocial insects

Eusocial insects provide special opportunities to elucidate the evolution of ageing as queens have apparently evaded costs of reproduction and reversed the fecundity-longevity trade-off generally observed in non-social organisms. But how reproduction affects longevity in eusocial insects has rarely been tested experimentally. In this study, we took advantage of the reproductive plasticity of workers to test the causal role of reproduction in determining longevity in eusocial insects. Using the eusocial bumblebee Bombus terrestris, we found that, in whole colonies, in which workers could freely 'choose' whether to become reproductive, workers' level of ovarian activation was significantly positively associated with longevity and ovary-active workers significantly outlived ovary-inactive workers. By contrast, when reproductivity was experimentally induced in randomly-selected workers, thereby decoupling it from other traits, workers' level of ovarian activation was significantly negatively associated with longevity and ovary-active workers were significantly less long-lived than ovary-inactive workers. These findings show that workers experience costs of reproduction and suggest that intrinsically high-quality individuals can overcome these costs. They also raise the possibility that eusocial insect queens exhibit condition-dependent longevity and hence call into question whether eusociality entails a truly reversed fecundity-longevity trade-off involving a fundamental remodelling of conserved genetic and endocrine networks underpinning ageing.

真社会性昆虫（Eusocial insects）为阐明衰老演化提供了独特契机，因为蜂后显然规避了繁殖代价，并逆转了非社会性生物中普遍存在的繁殖力-寿命权衡（fecundity-longevity trade-off）。然而，繁殖如何影响真社会性昆虫的寿命，这一问题鲜少得到实验验证。本研究借助工蜂的生殖可塑性（reproductive plasticity），探究了繁殖在真社会性昆虫寿命决定中的因果作用。本研究以真社会性的地熊蜂（Bombus terrestris）为实验对象，发现在完整蜂群中——此时工蜂可自由“选择”是否开启繁殖程序——工蜂的卵巢激活（ovarian activation）水平与寿命呈显著正相关，且卵巢激活的工蜂寿命显著长于未激活的个体。与之相反，当通过实验手段在随机选取的工蜂中诱导繁殖活性，从而将繁殖与其他性状解耦（decoupling）后，工蜂的卵巢激活水平与寿命呈显著负相关，且卵巢激活的工蜂寿命显著短于未激活的个体。上述结果表明，工蜂确实承受繁殖代价，同时也暗示内在品质优异的个体能够克服此类代价。本研究还提出了一种可能性：真社会性昆虫的蜂后可能存在条件依赖型寿命，进而对“真社会性是否真正逆转了繁殖力-寿命权衡”这一问题提出了质疑——该权衡涉及对衰老调控的保守遗传与内分泌网络（endocrine networks）的根本性重塑。