Amarasekare P
Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, California 92697, USA.
Theor Popul Biol. 1998 Feb;53(1):44-59. doi: 10.1006/tpbi.1997.1340.
Population persistence in patchy environments is expected to result from an interaction between local density dependence, dispersal, and spatial heterogeneity. Using two-patch models of single species, I explore two aspects of this interaction that have hitherto received little attention. First, how is the interaction affected when local density dependence changes from negative (logistic) to positive (Allee)? Second, how does dispersal mortality influence persistence ? When local dynamics are logistic, dispersal changes the strength of negative density dependence within patches without much between-patch effect. For example, dispersal mortality reduces the population growth rate and counteracts the tendency towards complex dynamics. Density-dependent disperal amplifies the nonlinearity in the growth rate, thus opposing the stabilizing effects of dispersal mortality. Spatial heterogeneity has little or no effect on stability. In contrast to the logistic, dispersal under Allee dynamics creates between-patch effects that bring about a qualitative change. Patches that fall below the Allee threshold are rescued from extinction by immigrants from patches that are above the threshold. Density-dependent dispersal enhances this rescue effect. Persistence below the extinction threshold is contingent on spatial heterogeneity. Dispersal mortality is of little or no consequence.
在斑块状环境中，种群的持续存在预计源于局部密度依赖、扩散和空间异质性之间的相互作用。利用单物种的双斑块模型，我探讨了这种相互作用中两个迄今很少受到关注的方面。第一，当局部密度依赖从负（逻辑斯谛）变为正（阿利效应）时，这种相互作用会受到怎样的影响？第二，扩散死亡率如何影响种群的持续存在？当局部动态为逻辑斯谛时，扩散会改变斑块内负密度依赖的强度，但斑块间的影响不大。例如，扩散死亡率会降低种群增长率，并抵消向复杂动态发展的趋势。密度依赖的扩散会放大增长率的非线性，从而对抗扩散死亡率的稳定作用。空间异质性对稳定性影响很小或没有影响。与逻辑斯谛情况相反，在阿利效应动态下的扩散会产生斑块间的影响，从而带来质的变化。低于阿利阈值的斑块会被高于阈值的斑块中的移民拯救，从而免于灭绝。密度依赖的扩散会增强这种拯救效应。低于灭绝阈值时的种群持续存在取决于空间异质性。扩散死亡率的影响很小或没有影响。
