Why and how does sociality change the fecundity/longevity trade-off in termites?

老龄化和生育力/寿命的权衡是直接相关的，因为生育力的增加与寿命的减少有关。然而，社会性昆虫表明这不是一个普遍的生物学规则。白蚁、蚂蚁或蜜蜂的蚁后具有非凡的繁殖率，是最长寿的昆虫之一。更惊人的是，繁殖实际上增加了寿命。在所有社会性昆虫中，这种生育力/寿命权衡的明显逆转的重复、趋同进化表明，社会性因果地重塑了这种基本的生活史权衡。然而，为什么以及如何做到这一点，仍然不清楚。第一个供资阶段的模拟项目的一个主要发现是，工人的生殖潜力（即，工人生育后代的可能性）是种性老化率的主要决定因素。工蜂的生殖潜力下降--通常与社会复杂性相关--预计会增加蜂王相对于工蜂的寿命。这些预测对应于我们发现经验的两种白蚁。在一个有不育工蚁的物种（Macrotermes bellicosus）中，在生殖动物的基因表达水平上没有检测到衰老的证据，而工蚁则显示出强烈的衰老迹象。相比之下，我们发现完全相反的一个物种（Cryptotermes secundus），其中生殖发育从全能工人。在第二个资助阶段，我们想测试这些发现的一般性，通过比较研究白蚁物种中的工人的生殖潜力不同。作为外群，我们使用它们的姐妹分类单元的代表，木脊虎。通过涵盖整个白蚁的生殖发育并考虑混杂因素，如菌落大小或物种和种姓特定的生态，我们将（i）通过进行转录组研究，分析生殖力/寿命权衡的分子机制如何随着社会性和/或工人的生殖潜力的增加而变化，以及（ii）具体模拟不同社会性的生殖力/寿命权衡的演变，考虑到白蚁的特性。因此，我们的项目链接的结果，从第一个融资阶段的近似框架与最终的观点。此外，它将其规模从白蚁社会性光谱两端的两个物种扩展到涵盖所有社会过渡的代表性物种范围。通过这样做，我们的项目将通过使用最古老的社会性昆虫谱系白蚁作为测试案例，为社会性如何以及为什么改变生育力/寿命权衡-从而老化-提供基本见解。

Ageing and the fecundity/longevity trade-off are directly linked as an increase in fecundity is associated with lifespan reduction. However, social insects illustrate this is not a universal biological rule. Queens of termites, ants or honey bees have extraordinary reproductive rates and are amongst the most long-living insects. Even more striking, reproduction actually increases longevity. The repeated, convergent evolution of this apparent reversal of the fecundity/longevity trade-off in all social insects suggests that sociality causally reshapes this fundamental life-history trade-off. Yet, why and how it does, remains unclear. One major finding from the modelling project of the first funding phase was that the reproductive potential of workers (i.e., the probability that a worker produces offspring) is a main determinant of caste-specific ageing rates. Declining workers’ reproductive potential – which commonly correlates with social complexity - is predicted to increase the lifespan of queens relative to that of workers. These predictions correspond to what we found empirically for two termite species. In a species with sterile workers (Macrotermes bellicosus), no evidence of ageing was detected at the gene expression level in reproductives, while workers showed strong signs of ageing. By contrast, we found exactly the reverse for a species (Cryptotermes secundus) in which reproductives develop from totipotent workers.During the second funding phase, we want to test these findings for generality by comparatively studying termite species in which the worker’s reproductive potential differs. As outgroup we use a representative of their sister taxon, the woodroaches. By covering the whole termite phylogeny and considering confounding factors, such as colony size or species- and caste-specific ecology, we will (i) analyse how molecular mechanisms that underlie the fecundity/longevity trade-off change with increasing sociality and / or worker’s reproductive potential by undertaking transcriptome studies, and (ii) specifically model the evolution of the fecundity/longevity trade-off with varying sociality, taking into account idiosyncrasies of termites. Therefore, our project links results from the proximate framework of the first funding phase with those of the ultimate perspective. Additionally, it extends its scale from two species at opposite ends of termites’ sociality spectrum to a representative range of species covering all social transitions. By doing this, our project will contribute fundamental insights into how and why sociality changes the fecundity/longevity trade-off - and thus ageing – by using the oldest social insect lineage, the termites, as a test case.