Edwards Phoebe D, Boonstra Rudy, Oli Madan K
Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.
Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, Florida, USA.
Ecology. 2023 Apr;104(4):e4008. doi: 10.1002/ecy.4008. Epub 2023 Mar 8.
Wild mammal populations exhibit a variety of dynamics, ranging from fairly stable with little change in population size over time to high-amplitude cyclic or erratic fluctuations. A persistent question in population ecology is why populations fluctuate as they do. Answering this seemingly simple question has proven to be challenging. Broadly, density-dependent feedback mechanisms should allow populations to grow at low density and slow or halt growth at high density. However, experimental tests of what demographic processes result in density-dependent feedback and on what timescale have proven elusive. Here, we used replicated density perturbation experiments and capture-mark-recapture analyses to test density-dependent population growth in populations of meadow voles (Microtus pennsylvanicus) during the summer breeding season by manipulating founding population density and observing the pattern of survival, reproduction, and population growth. High population density had no consistent effect on survival rates but generally negatively influenced recruitment and population growth rates. However, these density-dependent effects varied within the breeding season and across years. Our study provides evidence that density-dependent feedback mechanisms operate at finer time scales than previously believed and that process, additively with delayed year effects, is key to understanding multiyear population demography.
野生哺乳动物种群呈现出多种动态变化，从随时间推移种群数量变化不大的相对稳定状态到高振幅周期性或无规律波动。种群生态学中一个长期存在的问题是，种群为何会如此波动。事实证明，回答这个看似简单的问题颇具挑战性。一般来说，密度依赖反馈机制应使种群在低密度时增长，在高密度时减缓或停止增长。然而，关于哪些人口统计学过程导致密度依赖反馈以及在何种时间尺度上起作用的实验测试一直难以捉摸。在此，我们通过操纵初始种群密度并观察存活、繁殖和种群增长模式，利用重复密度扰动实验和标记重捕分析来测试夏季繁殖季节草甸田鼠（Microtus pennsylvanicus）种群中的密度依赖种群增长。高种群密度对存活率没有一致影响，但通常对补充率和种群增长率有负面影响。然而，这些密度依赖效应在繁殖季节内和多年间有所不同。我们的研究提供了证据，表明密度依赖反馈机制在比先前认为的更精细的时间尺度上起作用，并且该过程与延迟的年份效应相加，是理解多年种群统计学的关键。
