Kneitel Jamie M, Miller Thomas E
Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA.
Am Nat. 2003 Aug;162(2):165-71. doi: 10.1086/376585. Epub 2003 Jul 16.
Dispersal among local communities can have a variety of effects on species composition and diversity at local and regional scales. Local conditions (e.g., resource and predator densities) can have independent effects, as well as interact with dispersal, to alter these patterns. Based on metacommunity models, we predicted that local diversity would show a unimodal relationship with dispersal frequency. We manipulated dispersal frequencies, resource levels, and the presence of predators (mosquito larvae) among communities found in the water-filled leaves of the pitcher plant Sarracenia purpurea. Diversity and abundance of species of the middle trophic level, protozoa and rotifers, were measured. Increased dispersal frequencies significantly increased regional species richness and protozoan abundance while decreasing the variance among local communities. Dispersal frequency interacted with predation at the local community scale to produce patterns of diversity consistent with the model. When predators were absent, we found a unimodal relationship between dispersal frequency and diversity, and when predators were present, there was a flat relationship. Intermediate dispersal frequencies maintained some species in the inquiline communities by offsetting extinction rates. Local community composition and the degree of connectivity between communities are both important for understanding species diversity patterns at local and regional scales.
本地群落间的扩散会对局部和区域尺度上的物种组成及多样性产生多种影响。局部条件（如资源和捕食者密度）既能产生独立影响，也能与扩散相互作用，从而改变这些模式。基于集合群落模型，我们预测局部多样性与扩散频率将呈现单峰关系。我们在紫瓶子草充满水的叶片中发现的群落间操纵了扩散频率、资源水平以及捕食者（蚊子幼虫）的存在情况。对处于中间营养级的原生动物和轮虫的物种多样性及丰度进行了测量。扩散频率的增加显著提高了区域物种丰富度和原生动物丰度，同时降低了局部群落间的方差。在局部群落尺度上，扩散频率与捕食相互作用，产生了与模型一致的多样性模式。当没有捕食者时，我们发现扩散频率与多样性之间存在单峰关系，而当有捕食者时，则呈现平直线关系。中等扩散频率通过抵消灭绝率，使一些物种得以在寄居群落中维持。局部群落组成以及群落间的连通程度对于理解局部和区域尺度上的物种多样性模式都很重要。
