Amarasekare Priyanga
Department of Ecology and Evolution, The University of Chicago, 1101 East 57th Street, Chicago IL 60637, USA.
J Theor Biol. 2004 Jan 21;226(2):159-68. doi: 10.1016/j.jtbi.2003.08.007.
I investigate two aspects of source-sink theory that have hitherto received little attention: density-dependent dispersal and the cost of dispersal to sources. The cost arises because emigration reduces the per capita growth rate of sources, thus predisposing them to extinction. I show that source-sink persistence depends critically on the interplay between these two factors. When the emigration rate increases with abundance at an accelerating rate, dispersal costs to sources is the lowest and risk of source-sink extinction the least. When the emigration rate increases with abundance at a decelerating rate, dispersal costs to sources is the highest and the risk of source-sink extinction the greatest. Density-independent emigration has an intermediate effect. Thus, density-dependent dispersal per se does not increase or decrease source-sink persistence relative to density-independent dispersal. The exact mode of dispersal is crucial. A key point to appreciate is that these effects of dispersal on source-sink extinction arise from the temporal density-dependence that dispersal induces in the per capita growth rates of source and sink populations. Temporal density-dependence due to dispersal is beneficial at low abundances because it rescues sinks from extinction, and detrimental at high abundances because it drives otherwise viable sources to extinction. These results are robust to the nature of population dynamics in the sink, whether exponential or logistic. They provide a means of assessing the relative costs and benefits of preserving sink habitats given three biological parameters.
我研究了源 - 汇理论中两个迄今为止很少受到关注的方面：密度依赖型扩散以及扩散对源的代价。这种代价之所以产生，是因为迁出会降低源的人均增长率，从而使它们更容易灭绝。我表明，源 - 汇的持久性关键取决于这两个因素之间的相互作用。当迁出率随着丰度以加速的速率增加时，对源的扩散代价最低，源 - 汇灭绝的风险也最小。当迁出率随着丰度以减速的速率增加时，对源的扩散代价最高，源 - 汇灭绝的风险也最大。与密度无关的迁出具有中间效应。因此，相对于与密度无关的扩散而言，密度依赖型扩散本身并不会增加或降低源 - 汇的持久性。扩散的具体模式至关重要。需要认识到的一个关键点是，扩散对源 - 汇灭绝的这些影响源于扩散在源和汇种群的人均增长率中所诱导的时间密度依赖性。由于扩散导致的时间密度依赖性在低丰度时是有益的，因为它能使汇免于灭绝，而在高丰度时是有害的，因为它会使原本可行的源走向灭绝。这些结果对于汇中种群动态的性质（无论是指数型还是逻辑斯蒂型）都是稳健的。它们提供了一种在给定三个生物学参数的情况下评估保护汇栖息地的相对成本和收益的方法。
