Data from: Population and life-history consequences of within-cohort individual variation

The consequences of within-cohort (i.e., among-individual) variation for population dynamics are poorly understood, in particular for the case where life history is density dependent. We develop a physiologically structured population model that incorporates individual variation among and within cohorts and that allows us to explore the intertwined relationship between individual life history and population dynamics. Our model is parameterized for the lizard Zootoca vivipara and reproduces well the species' dynamics and life history. We explore two common mechanisms that generate within-cohort variation: variability in food intake and variability in birth date. Predicted population dynamics are inherently very stable and do not qualitatively change when either of these sources of individual variation is introduced. However, increased within-cohort variation in food intake leads to changes in morphology with longer but skinnier individuals, even though mean food intake does not change. Morphological changes result from a seemingly universal non-linear relationship between growth and resource availability, but may only become apparent in environments with strongly fluctuating resources. Overall, our results highlight the importance of using a mechanistic framework to gain insights into how different sources of intraspecific variability translate into life-history and population dynamic changes.同队列（即个体间）变异对种群动态的影响迄今尚未得到充分阐释，尤其是当物种生活史存在密度依赖性的情境下。我们构建了一款可纳入队列间与队列内个体变异的生理结构种群模型（physiologically structured population model），借此得以深入探究个体生活史与种群动态之间的复杂相互关联。我们以胎生蜥蜴（Zootoca vivipara）为研究对象完成模型参数化，且该模型能够精准复现该物种的种群动态与生活史特征。我们探究了两种常见的同队列变异产生机制：食物摄入变异性与出生时间变异性。模型预测的种群动态本身具备极强的稳定性，即便引入任意一种个体变异来源，其动态特征也不会发生质的改变。然而，即便平均食物摄入量保持恒定，同队列内食物摄入变异程度的提升会引发种群形态改变：个体体型变长但更为纤细。此类形态变化源于生长与资源可获得性之间看似普遍存在的非线性关系，但仅在资源剧烈波动的环境中才会显现。总体而言，本研究结果凸显了采用机制性研究框架的重要性，借此可深入理解不同来源的种内变异如何转化为生活史与种群动态的变化。