Fluctuating population density in stochastic environments can contribute to maintain life-history variation within populations via density-dependent selection. We used individual-based data from a population of Soay sheep to examine variation in life-history strategies at high and low population density. We incorporated life-history trade-offs among survival, reproduction and body mass growth into structured population models and found support for the prediction that different life-history strategies are optimal at low and high population densities. Shorter generation times and lower asymptotic body mass were selected for in high-density environments even though heavier individuals had higher probabilities to survive and reproduce. In contrast, greater asymptotic body mass and longer generation times were optimal at low population density. If populations fluctuate between high density when resources are scarce, and low densities when they are abundant, the variation in density will generate fluctuating selection for different life-history strategies, that could act to maintain life-history variation.

中文翻译：

---

在有食物限制的有蹄类动物种群中，生活史策略会随着竞争的激烈程度而变化。

随机环境中不断变化的种群密度可以通过依赖于密度的选择来维持种群内的生活史变化。我们使用了来自Soay绵羊种群的基于个人的数据来研究高种群密度和低种群密度下生活史策略的变化。我们将生存，繁殖和体重增长之间的生活史权衡取舍到结构化的人口模型中，并为不同的生活史策略在低密度和高密度下的最佳预测提供了支持。即使在较重的个体中，生存和繁殖的概率较高，但在高密度环境中选择了较短的生成时间和较低的渐近体重。相反，在低人口密度下，更大的渐近体重和更长的生成时间是最佳的。