Sullivan Lauren L, Li Bingtuan, Miller Tom E X, Neubert Michael G, Shaw Allison K
Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN 55108;
Department of Mathematics, University of Louisville, Louisville, KY 40292.
Proc Natl Acad Sci U S A. 2017 May 9;114(19):5053-5058. doi: 10.1073/pnas.1618744114. Epub 2017 Apr 25.
Density dependence plays an important role in population regulation and is known to generate temporal fluctuations in population density. However, the ways in which density dependence affects spatial population processes, such as species invasions, are less understood. Although classical ecological theory suggests that invasions should advance at a constant speed, empirical work is illuminating the highly variable nature of biological invasions, which often exhibit nonconstant spreading speeds, even in simple, controlled settings. Here, we explore endogenous density dependence as a mechanism for inducing variability in biological invasions with a set of population models that incorporate density dependence in demographic and dispersal parameters. We show that density dependence in demography at low population densities-i.e., an Allee effect-combined with spatiotemporal variability in population density behind the invasion front can produce fluctuations in spreading speed. The density fluctuations behind the front can arise from either overcompensatory population growth or density-dependent dispersal, both of which are common in nature. Our results show that simple rules can generate complex spread dynamics and highlight a source of variability in biological invasions that may aid in ecological forecasting.
密度依赖在种群调节中起着重要作用，并且已知会在种群密度中产生时间波动。然而，密度依赖影响空间种群过程（如物种入侵）的方式却鲜为人知。尽管经典生态学理论认为入侵应以恒定速度推进，但实证研究正在揭示生物入侵的高度可变性质，即使在简单、可控的环境中，生物入侵也常常表现出非恒定的传播速度。在这里，我们利用一组在人口统计学和扩散参数中纳入密度依赖的种群模型，探索内源性密度依赖作为一种导致生物入侵变异性的机制。我们表明，低种群密度下人口统计学中的密度依赖——即阿利效应——与入侵前沿后方种群密度的时空变异性相结合，会导致传播速度出现波动。前沿后方的密度波动可能源于过度补偿性种群增长或密度依赖扩散，这两者在自然界中都很常见。我们的结果表明，简单的规则可以产生复杂的传播动态，并突出了生物入侵变异性的一个来源，这可能有助于生态预测。
