Community dynamics in a heterogeneous environment. And subsidized effects by dispersal

我们研究了区域持久性的本地非永久性社区是否可以分散的组成种群在一个异质性的环境，具有不同的栖息地。对于两个具有饱和功能反应的消费者共享同一资源，当上级本地竞争者的扩散率超过下级竞争者时，共存得以实现。如果栖息地的生产力不同，则会出现人口从生产力较高的栖息地流向生产力较低的栖息地，并形成源-汇结构。因此，竞争在生产力较高的地方释放，两个消费者在两个栖息地的种群振荡是同步的，这种共存不是由于许多空间模型中观察到的空间竞争，我们对两个食饵共享一个commoc捕食者并表现出明显的竞争也有类似的结果。因此，如果扩散是扩散性的，没有出现空的栖息地，同样的机制可以允许区域共存，无论竞争是否直接或间接发生在三个营养级的食物链中，在较高的营养级的种群移动引起的自上而下的影响，在贫瘠的栖息地。另一方面，较低营养级种群的移动产生自下而上的效应，并促进较高营养级种群的持续存在。因此，生境的空间异质性以及资源和生物的移动可能有助于延长食物链

We examined whether regional persistence of locally impermanent communities can be possible by dispersal of constituent populations in a heterogeneous environment with qualitatively different habitats. For two consumers sharing a common resource with saturating functional responses, coexistence is realized when the dispersal rate of the superior local competitor exceeds that of the inferior. If the habitats differ in produativity, there appear population flows from the more productive habitat to the less productive and they create the source-sink structure. Thus, compettion is released in the more productive and population oscillations of the two consumers in the two consumers in the two habitats are synchronous, the coexistence is not due to the spatial asynchrony observed in many spatial models.We have similar results for two prey sharing a commoc predator and exhibiting apparent competition. Therefore, if the dispersal is diffusive and there appear no empty habitats, the same mechanism can allow regional coexistence irrespective of whether competiton occurs directly or indirectlyIn three-trophic-level food chains, movement of populations in a higher trophic level causes top-down effects in sterile habitats. On the other hand, movement of populations in a lower trophic level generates bottom-up effects and promotes persistence of populations in higher trophic levels. Thus, spatial heterogeneity of habitats and movements of resoueces and organisms may contribute to lengthen the food chains