Data from: The effect of dietary restriction on reproduction: a meta-analytic perspective

Background: Dietary restriction (DR), a reduction in the amount of food or particular nutrients eaten, is the most consistent environmental manipulation to extend lifespan and protect against age related diseases. Current evolutionary theory explains this effect as a shift in the resolution of the trade-off between lifespan and reproduction. However, recent studies have questioned the role of reproduction in mediating the effect of DR on longevity and no study has quantitatively investigated the effect of DR on reproduction across species. Results: Here we report a comprehensive comparative meta-analysis of the effect of DR on reproduction. In general, DR reduced reproduction across taxa, but several factors moderated this effect. The effect of DR on reproduction was greater in well-studied model species (yeast, nematode worms, fruit flies and rodents) than non-model species. This mirrors recent results for longevity and, for reproduction, seems to result from a faster rate of decline with decreasing resources in model species. Our results also suggested that not all reproductive traits are affected equally by DR. High and moderate cost reproductive traits suffered a significant reduction with DR, but low cost traits, such as ejaculate production, did not. Although the effect of DR on reproduction was stronger in females than males, this sex difference reduced to near zero when accounting for other co-factors such as the costliness of the reproductive trait. Thus, sex differences in the effect of DR on longevity may be due to a failure to expose males to as complete a range of the costs of reproduction as females. Conclusions: We suggest that to better understand the generality of the effect of DR, future studies should attempt to address the cause of the apparent model species bias and ensure that individuals are exposed to as many of the costs of reproduction as possible. Furthermore, our meta-analytic approach reveals a general shortage of DR studies that record reproduction, particularly in males, as well as a lack of direct side-by-side comparisons of the effect of DR on males and females.

背景：饮食限制（Dietary restriction, DR）指减少食物摄入量或特定营养摄入，是目前已知最稳定的可延长寿命、抵御年龄相关疾病的环境干预手段。当前进化理论将该效应归因于寿命与繁殖之间权衡关系的动态调整。然而，近期研究对繁殖在介导饮食限制对寿命的影响中的作用提出了质疑，且目前尚无研究对跨物种的饮食限制对繁殖的影响进行定量分析。
结果：本研究针对饮食限制对繁殖的影响开展了全面的比较元分析（meta-analysis）。总体而言，饮食限制会降低各生物类群的繁殖能力，但该效应受到多种因素的调节。相较于非模式物种，饮食限制对繁殖的影响在研究较为深入的模式物种（酵母、线虫、果蝇与啮齿类）中更为显著。这一现象与此前关于寿命的研究结果一致，而就繁殖而言，该现象似乎源于模式物种在资源减少时繁殖能力下降速率更快。研究结果同时表明，并非所有繁殖性状均会受到饮食限制的同等影响：高成本与中等成本的繁殖性状会因饮食限制出现显著衰退，而低成本性状（如精液产出）则未受明显影响。尽管饮食限制对雌性繁殖的影响强于雄性，但在纳入繁殖性状成本等其他协同因子后，这种性别差异会趋近于消失。因此，饮食限制对寿命的影响存在性别差异，可能是由于雄性未像雌性那样暴露于完整范围的繁殖成本之中。
结论：本研究认为，若要更好地理解饮食限制效应的普遍性，未来研究应尝试阐明模式物种偏差产生的原因，并确保研究对象尽可能多地承受繁殖成本。此外，本元分析方法还揭示出当前饮食限制研究普遍存在两个短板：一是鲜有研究记录雄性的繁殖情况，二是缺乏对饮食限制在雌雄个体上的影响进行直接的平行对照比较。