Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
Department of Biology, Queen's University, Kingston, ON, Canada.
J Evol Biol. 2024 Nov 2;37(11):1244-1263. doi: 10.1093/jeb/voae107.
Individual vital rates, such as mortality and birth rates, are key determinants of lifetime reproductive success, and variability in these rates shapes population dynamics. Previous studies have found that this vital rate heterogeneity can influence demographic properties, including population growth rates. However, the explicit effects of the variation within and the covariance between vital rates that can also vary throughout the lifespan on population growth remain unknown. Here, we explore the analytical consequences of nongenetic heterogeneity on long-term population growth rates and rates of evolution by modifying traditional age-structured population projection matrices to incorporate variation among individual vital rates. The model allows vital rates to be permanent throughout life ("fixed condition") or to change over the lifespan ("dynamic condition"). We reduce the complexity associated with adding individual heterogeneity to age-structured models through a novel application of matrix collapsing ("phenotypic collapsing"), showing how to collapse in a manner that preserves the asymptotic and transient dynamics of the original matrix. The main conclusion is that nongenetic individual heterogeneity can strongly impact the long-term growth rate and rates of evolution. The magnitude and sign of this impact depend heavily on how the heterogeneity covaries across the lifespan of an organism. Our results emphasize that nongenetic variation cannot simply be viewed as random noise, but rather that it has consistent, predictable effects on fitness and evolvability.
个体生命参数，如死亡率和出生率，是决定终生生殖成功的关键因素，而这些参数的变化塑造了种群动态。先前的研究发现，这种生命参数异质性可以影响人口属性，包括人口增长率。然而，在整个生命周期内变化的生命参数的内部和协方差的明确影响，以及对人口增长的影响仍然未知。在这里，我们通过修改传统的年龄结构人口预测矩阵来研究非遗传异质性对长期人口增长率和进化率的分析后果，以纳入个体生命参数之间的变化。该模型允许生命参数在整个生命周期内保持不变（“固定条件”）或随生命周期而变化（“动态条件”）。我们通过矩阵压缩（“表型压缩”）的新应用，降低了将个体异质性添加到年龄结构模型中的复杂性，展示了如何以保留原始矩阵的渐近和瞬态动力学的方式进行压缩。主要结论是非遗传个体异质性会强烈影响长期增长率和进化率。这种影响的大小和方向在很大程度上取决于异质性在生物体生命周期中的变化方式。我们的研究结果强调，非遗传变异不能简单地视为随机噪声，而是对适应性和可进化性具有一致的、可预测的影响。
