Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
Proc Natl Acad Sci U S A. 2017 Oct 31;114(44):11582-11590. doi: 10.1073/pnas.1710679114. Epub 2017 Oct 10.
We analyze the stochastic demography and evolution of a density-dependent age- (or stage-) structured population in a fluctuating environment. A positive linear combination of age classes (e.g., weighted by body mass) is assumed to act as the single variable of population size, [Formula: see text], exerting density dependence on age-specific vital rates through an increasing function of population size. The environment fluctuates in a stationary distribution with no autocorrelation. We show by analysis and simulation of age structure, under assumptions often met by vertebrate populations, that the stochastic dynamics of population size can be accurately approximated by a univariate model governed by three key demographic parameters: the intrinsic rate of increase and carrying capacity in the average environment, [Formula: see text] and [Formula: see text], and the environmental variance in population growth rate, [Formula: see text] Allowing these parameters to be genetically variable and to evolve, but assuming that a fourth parameter, [Formula: see text], measuring the nonlinearity of density dependence, remains constant, the expected evolution maximizes [Formula: see text] This shows that the magnitude of environmental stochasticity governs the classical trade-off between selection for higher [Formula: see text] versus higher [Formula: see text] However, selection also acts to decrease [Formula: see text], so the simple life-history trade-off between [Formula: see text]- and [Formula: see text]-selection may be obscured by additional trade-offs between them and [Formula: see text] Under the classical logistic model of population growth with linear density dependence ([Formula: see text]), life-history evolution in a fluctuating environment tends to maximize the average population size.
我们分析了在波动环境中具有密度依赖性的年龄（或阶段）结构种群的随机动态和进化。假设年龄类别的正线性组合（例如，按体重加权）作为种群大小的单一变量，[公式：见正文]，通过种群大小的递增函数对特定年龄的重要率施加密度依赖性。环境以无自相关的稳定分布波动。我们通过对年龄结构的分析和模拟表明，在通常满足脊椎动物种群的假设下，种群大小的随机动态可以通过由三个关键人口统计参数控制的单变量模型来准确逼近：平均环境中的固有增长率和承载能力，[公式：见正文]和[公式：见正文]，以及种群增长率的环境方差，[公式：见正文]允许这些参数具有遗传可变性并进化，但假设第四个参数，[公式：见正文]，测量密度依赖性的非线性，保持不变，预期的进化最大化[公式：见正文]这表明环境随机性的大小决定了选择更高[公式：见正文]与更高[公式：见正文]之间的经典权衡。然而，选择也作用于降低[公式：见正文]，因此，[公式：见正文]-和[公式：见正文]-选择之间的简单生活史权衡可能会被它们与[公式：见正文]之间的额外权衡所掩盖。在具有线性密度依赖性的经典逻辑斯谛种群增长模型下([公式：见正文])，波动环境中的生活史进化倾向于最大化平均种群大小。
