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

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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