UMR CNRS 6282 BioGéoSciences, Équipe Écologie Évolutive, Université Bourgogne-Franche Comté, Dijon, France.
BMC Evol Biol. 2020 Feb 3;20(1):18. doi: 10.1186/s12862-020-1586-x.
The disposable soma theory of ageing assumes that organisms optimally trade-off limited resources between reproduction and longevity to maximize fitness. Early reproduction should especially trade-off against late reproduction and longevity because of reduced investment into somatic protection, including immunity. Moreover, as optimal reproductive strategies of males and females differ, sexually dimorphic patterns of senescence may evolve. In particular, as males gain fitness through mating success, sexual competition should be a major factor accelerating male senescence. In a single experiment, we examined these possibilities by establishing artificial populations of the mealworm beetle, Tenebrio molitor, in which we manipulated the sex-ratio to generate variable levels of investment into reproductive effort and sexual competition in males and females.
As predicted, variation in sex-ratio affected male and female reproductive efforts, with contrasted sex-specific trade-offs between lifetime reproduction, survival and immunity. High effort of reproduction accelerated mortality in females, without affecting immunity, but high early reproductive success was observed only in balanced sex-ratio condition. Male reproduction was costly on longevity and immunity, mainly because of their investment into copulations rather than in sexual competition.
Our results suggest that T. molitor males, like females, maximize fitness through enhanced longevity, partly explaining their comparable longevity.
衰老的一次性躯体理论假设，生物在繁殖和寿命之间最优地权衡有限的资源，以最大化适应度。早期繁殖应该特别权衡晚期繁殖和寿命，因为减少了对躯体保护的投资，包括免疫。此外，由于雄性和雌性的最优繁殖策略不同，衰老的性二态模式可能会进化。特别是，由于雄性通过交配成功获得适应度，性竞争应该是加速雄性衰老的主要因素。在一项单独的实验中，我们通过建立黄粉虫（Tenebrio molitor）的人工种群来检验这些可能性，在这些种群中，我们操纵性别比例，以产生雄性和雌性生殖努力和性竞争的可变投资水平。
正如预测的那样，性别比例的变化影响了雄性和雌性的生殖努力，表现出寿命繁殖、生存和免疫之间的性别特异性权衡。高生殖努力加速了雌性的死亡率，而不影响免疫，但只有在性别比例平衡的情况下才观察到高早期生殖成功。雄性生殖对寿命和免疫有代价，主要是因为它们将投资用于交配而不是性竞争。
我们的结果表明，T. molitor 雄性，像雌性一样，通过增强寿命来最大化适应度，这部分解释了它们相当的寿命。
