Data from: Evolution of male age-specific reproduction under differential risks and causes of death: males pay the cost of high female fitness

Classic theories of ageing evolution predict that increased extrinsic mortality due to an environmental hazard selects for increased early reproduction, rapid ageing and short intrinsic lifespan. Conversely, emerging theory maintains that when ageing increases susceptibility to an environmental hazard, increased mortality due to this hazard can select against ageing in physiological condition and prolong intrinsic lifespan. However, evolution of slow ageing under high-condition-dependent mortality is expected to result from reallocation of resources to different traits and such reallocation may be hampered by sex-specific trade-offs. Because same life-history trait values often have different fitness consequences in males and females, sexually antagonistic selection can preserve genetic variance for lifespan and ageing. We previously showed that increased condition-dependent mortality caused by heat shock leads to evolution of long-life, decelerated late-life mortality in both sexes and increased female fecundity in the nematode, Caenorhabditis remanei. Here, we used these cryopreserved lines to show that males evolving under heat shock suffered from reduced early-life and net reproduction, while mortality rate had no effect. Our results suggest that heat-shock resistance and associated long-life trade-off with male, but not female, reproduction and therefore sexually antagonistic selection contributes to maintenance of genetic variation for lifespan and fitness in this population.衰老演化的经典理论预测：当环境危害导致外源死亡率升高时，自然选择会青睐早期繁殖能力增强、衰老速率加快且固有寿命更短的个体。与之相对，新兴演化理论则提出，若衰老会提升个体对某一环境危害的易感性，那么该危害引发的死亡率上升，反而会通过生理层面的选择抑制衰老进程，并延长固有寿命。不过，在高条件依赖型死亡率情境下演化出的慢衰老表型，往往源于资源向不同性状的重新分配，而这种资源重分配可能会受到性特异性权衡的阻碍。由于同一生活史性状在雌雄个体中通常会产生不同的适合度效应，因此性拮抗选择能够维持寿命与衰老相关的遗传变异。 我们此前的研究表明，在雷氏隐杆线虫（Caenorhabditis remanei）中，热激引发的条件依赖型死亡率升高，会促使雌雄个体均演化出长寿命、晚年死亡率减缓的表型，同时提升雌性繁殖力。 本研究利用这些冷冻保存的实验品系，发现经热激筛选演化的雄性个体，其早期繁殖力与总繁殖力均出现下降，而死亡率则未受显著影响。本研究结果提示，热激抗性与长寿命表型之间存在与雄性繁殖力相关的演化权衡（而与雌性繁殖力无关），因此性拮抗选择有助于维持该种群中寿命与适合度相关的遗传变异。