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，群居昆虫表明，这并不是一条普遍的生物学规则。白蚁、蚂蚁或蜜蜂的蜂王具有非凡的繁殖率，是最长寿的昆虫之一。更引人注目的是，繁殖实际上延长了寿命。在所有社会性昆虫中，这种明显的繁殖力/寿命权衡的明显逆转的反复、趋同的进化表明，社会性因果地重塑了这一基本的生活史权衡。然而，它为什么以及如何做到这一点，目前尚不清楚。第一个供资阶段的模型项目的一个主要发现是，工人的生殖潜力(即工人生育后代的概率)是特定种姓老龄化速度的主要决定因素。据预测，与工蜂相比，蜂王的寿命会延长。这种下降通常与社会复杂性有关。这些预测与我们对两种白蚁的经验发现相一致。在具有不育工蚁(Macrotermes Belicosus)的物种中，在繁殖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，我们发现了完全相反的物种(隐白蚁Secundus)，其中生殖器是从全能的工蚁发育而来的。在第二个资助阶段，我们想通过比较研究工蚁繁殖潜力不同的白蚁物种来测试这些发现的普遍性。作为外类群，我们使用了它们的姊妹分类单元的代表--伍德罗奇。通过涵盖整个白蚁系统发育和考虑混杂因素，如群体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，分析导致繁殖力/寿命权衡的分子机制如何随着社会性和/或工蚁生殖潜力的增加而变化，以及(Ii)考虑白蚁的特性，具体模拟不同社会性的繁殖力/寿命权衡的进化。因此，我们的项目将第一个筹资阶段的初步框架的结果与最终前景的结果联系起来。此外，它还将其规模从白蚁社会性光谱的两端的两个物种扩展到涵盖所有社会转型的代表性物种范围。通过这样做，我们的项目将通过使用最古老的社会昆虫谱系白蚁作为测试案例，对社会性如何以及为什么改变生殖力/寿命的权衡--从而改变衰老--提供基本的见解。

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.