Department of Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA, UK.
Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, Charlotte Auerbach Road, Edinburgh, EH9 3FL, UK.
Ecol Lett. 2019 Aug;22(8):1203-1213. doi: 10.1111/ele.13275. Epub 2019 May 20.
A trade-off between current and future fitness potentially explains variation in life-history strategies. A proposed mechanism behind this is parasite-mediated reproductive costs: individuals that allocate more resources to reproduction have fewer to allocate to defence against parasites, reducing future fitness. We examined how reproduction influenced faecal egg counts (FEC) of strongyle nematodes using data collected between 1989 and 2008 from a wild population of Soay sheep in the St. Kilda archipelago, Scotland (741 individuals). Increased reproduction was associated with increased FEC during the lambing season: females that gave birth, and particularly those that weaned a lamb, had higher FEC than females that failed to reproduce. Structural equation modelling revealed future reproductive costs: a positive effect of reproduction on spring FEC and a negative effect on summer body weight were negatively associated with overwinter survival. Overall, we provide evidence that parasite resistance and body weight are important mediators of survival costs of reproduction.
在当前和未来适应度之间存在权衡，这可能解释了生活史策略的变化。这种权衡背后的一个提出的机制是寄生虫介导的生殖成本：那些将更多资源分配给生殖的个体，用于防御寄生虫的资源就会减少，从而降低未来的适应度。我们使用 1989 年至 2008 年间在苏格兰圣基尔达群岛的野生设得兰绵羊种群中收集的数据，研究了生殖如何影响强线虫的粪便卵计数（FEC）（741 只个体）。繁殖增加与产羔季节的 FEC 增加有关：分娩的母羊，特别是那些成功育有羔羊的母羊，其 FEC 高于未繁殖的母羊。结构方程模型揭示了未来的生殖成本：繁殖对春季 FEC 的正效应以及对夏季体重的负效应与冬季生存呈负相关。总的来说，我们提供的证据表明，寄生虫抗性和体重是生殖生存成本的重要中介因素。
