Department of Environmental Science and Policy, University of California, 1 Shields Avenue, Davis, California 95616, USA.
Ecology. 2011 Apr;92(4):859-70. doi: 10.1890/10-1095.1.
Dispersal among ecological communities is usually assumed to be random in direction, or to vary in distance or frequency among species. However, a variety of natural systems and types of organisms may experience dispersal that is biased by directional currents or by gravity on hillslopes. We developed a general model for competing species in metacommunities to evaluate the role of directionally biased dispersal on species diversity, abundance, and traits. In parallel, we tested the role of directionally biased dispersal on communities in a microcosm experiment with protists and rotifers. Both the model and experiment independently demonstrated that diversity in local communities was reduced by directionally biased dispersal, especially dispersal that was biased away from disturbed patches. Abundance of species (and composition) in local communities was a product of disturbance intensity but not dispersal directionality. High disturbance selected for species with high intrinsic growth rates and low competitive abilities. Overall, our conclusions about the key role of dispersal directionality in (meta)communities seem robust and general, since they were supported both by the model, which was set in a general framework and not parameterized to fit to a specific system, and by a specific experimental test with microcosms.
在生态群落中，扩散通常被认为是随机的方向，或者在物种之间的距离或频率上有所不同。然而，各种自然系统和生物类型可能会经历由定向流或山坡上的重力引起的偏向扩散。我们为元群落中的竞争物种开发了一个通用模型，以评估定向偏向扩散对物种多样性、丰度和特征的作用。与此同时，我们在一个含有原生动物和轮虫的微宇宙实验中测试了定向偏向扩散对群落的作用。模型和实验都独立地表明，局部群落的多样性因定向偏向扩散而减少，尤其是那些偏向于受干扰斑块的扩散。本地群落中物种的丰度（和组成）是干扰强度的产物，而不是扩散方向性的产物。高干扰选择了具有高内在增长率和低竞争能力的物种。总的来说，我们关于（元）群落中扩散方向性的关键作用的结论似乎是稳健和普遍的，因为它们既得到了模型的支持，该模型建立在一个通用框架中，并没有参数化来适应特定的系统，也得到了一个特定的微宇宙实验测试的支持。
