Density dependence in demography and dispersal generates fluctuating invasion speeds
Density dependence in demography and dispersal generates fluctuating invasion speeds
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DOI：
10.1073/pnas.1618744114
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发表时间：
2016-09
期刊：
影响因子：
--
通讯作者：
L. Sullivan;Bingtuan Li;T. Miller;M. Neubert;Allison K. Shaw
中科院分区：
文献类型：
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作者：
L. Sullivan;Bingtuan Li;T. Miller;M. Neubert;Allison K. Shaw
重要性减缓入侵物种的传播仍然很困难，入侵速度的实质性变化越来越多地被记录在案，但这种变化的来源知之甚少。我们报告了一种机制，入侵速度的变化。人口统计学中的密度依赖性和扩散的联合作用可以导致入侵波动，即使在恒定的环境中。速度波动是通过创造一个被推动的入侵波而发生的，这个入侵波不是从前沿的小种群向前移动，而是从更大、更成熟的种群向前“跳跃”越过先前的入侵前沿。推力强度的变化会产生波动的入侵速度。引起波动的条件在自然界中被广泛记录，这表明入侵变异性的一个重要来源可能被忽视。密度依赖在种群调节中起着重要作用，并且已知会产生种群密度的时间波动。然而，密度依赖性影响空间种群过程（如物种入侵）的方式却鲜为人知。虽然经典生态学理论认为入侵应该以恒定的速度前进，但经验工作正在阐明生物入侵的高度可变性，即使在简单的控制环境中，生物入侵也经常表现出不恒定的传播速度。在这里，我们探讨内源性密度依赖作为一种机制，诱导生物入侵的变异与一组人口模型，将密度依赖的人口和扩散参数。我们表明，在人口密度低的人口密度依赖，即，Allee效应--与入侵前沿后面的种群密度的时空变化相结合，可以产生传播速度的波动。锋面后的密度波动可能是由过度补偿的种群增长或密度依赖的扩散引起的，这两种情况在自然界中都很常见。我们的研究结果表明，简单的规则可以产生复杂的传播动力学和突出的生物入侵，可能有助于生态预测的变化来源。
Significance Mitigating the spread of invasive species remains difficult—substantial variability in invasion speed is increasingly well-documented, but the sources of this variability are poorly understood. We report a mechanism for invasion speed variability. The combined action of density dependence in demography and dispersal can cause invasions to fluctuate, even in constant environments. Speed fluctuations occur through creation of a pushed invasion wave that moves forward not from small populations at the leading edge but instead, from larger, more established populations that “jump” forward past the previous invasion front. Variability in strength of the push generates fluctuating invasion speeds. Conditions giving rise to fluctuations are widely documented in nature, suggesting that an important source of invasion variability may be overlooked. 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.