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Investigating the Dynamics of Elk Population Size and Body Mass in a Seasonal Environment Using a Mechanistic Integral Projection Model.
The American Naturalist ( IF 2.9 ) Pub Date : 2020-06-22 , DOI: 10.1086/708723
Shelly Lachish , Ellen E. Brandell , Meggan E. Craft , Andrew P. Dobson , Peter J. Hudson , Daniel R. MacNulty , Tim Coulson

Environmentally mediated changes in body size often underlie population responses to environmental change, yet this is not a universal phenomenon. Understanding when phenotypic change underlies population responses to environmental change is important for obtaining insights and robust predictions of population dynamics in a changing world. We develop a dynamic integral projection model that mechanistically links environmental conditions to demographic rates and phenotypic traits (body size) via changes in resource availability and individual energetics. We apply the model to the northern Yellowstone elk population and explore population responses to changing patterns of seasonality, incorporating the interdependence of growth, demography, and density-dependent processes operating through population feedback on available resources. We found that small changes in body size distributions can have large impacts on population dynamics but need not cause population responses to environmental change. Environmental changes that altered demographic rates directly, via increasing or decreasing resource availability, led to large population impacts in the absence of substantial changes to body size distributions. In contrast, environmentally driven shifts in body size distributions could occur with little consequence for population dynamics when the effect of environmental change on resource availability was small and seasonally restricted and when strong density-dependent processes counteracted expected population responses. These findings highlight that a robust understanding of how associations between body size and demography influence population responses to environmental change will require knowledge of the shape of the relationship between phenotypic distributions and vital rates, the population status with regard to its carrying capacity, and importantly the nature of the environmentally driven change in body size and carrying capacity.

中文翻译:

使用机械积分投影模型研究季节性环境中麋鹿种群大小和体重的动态。

人口规模对环境的影响通常是人口对环境变化的反应的基础,但这不是普遍现象。了解表型变化何时是人口对环境变化的反应的基础,对于在变化的世界中获得洞察力和对人口动态的可靠预测至关重要。我们开发了一个动态积分投影模型,该模型通过资源可用性和个体能量的变化将环境条件与人口统计学特征和表型特征(体型)机械地联系起来。我们将该模型应用于北部黄石麋鹿种群,并探索种群对季节性变化模式的反应,并通过对可用资源的种群反馈,结合了增长,人口统计学和密度依赖过程之间的相互依赖性。我们发现,身体大小分布的微小变化会对人口动态产生重大影响,但不必引起人口对环境变化的反应。环境变化通过增加或减少资源可利用性直接改变了人口比率,导致在没有大幅度改变身体大小分布的情况下对人口造成的巨大影响。相反,当环境变化对资源可利用性的影响较小且受季节限制,且密度依赖性强的过程抵消了预期的人口响应时,环境尺寸分布的变化可能不会对人口动态产生任何影响。
更新日期:2020-07-20
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