Schuler Matthew S, Chase Jonathan M, Knight Tiffany M
Department of Biology Washington University in St. Louis St. Louis MO USA.
Present address: Darrin Fresh Water Institute Department of Biology Rensselaer Polytechnic Institute Troy NY 12180.
Ecol Evol. 2017 Jun 17;7(15):5774-5783. doi: 10.1002/ece3.2858. eCollection 2017 Aug.
Increased dispersal of individuals among discrete habitat patches should increase the average number of species present in each local habitat patch. However, experimental studies have found variable effects of dispersal on local species richness. Priority effects, predators, and habitat heterogeneity have been proposed as mechanisms that limit the effect of dispersal on species richness. However, the size of a habitat patch could affect how dispersal regulates the number of species able to persist. We investigated whether habitat size interacted with dispersal rate to affect the number of species present in local habitats. We hypothesized that increased dispersal rates would positively affect local species richness more in small habitats than in large habitats, because rare species would be protected from demographic extinction. To test the interaction between dispersal rate and habitat size, we factorially manipulated the size of experimental ponds and dispersal rates, using a model community of freshwater zooplankton. We found that high-dispersal rates enhanced local species richness in small experimental ponds, but had no effect in large experimental ponds. Our results suggest that there is a trade-off between patch connectivity (a mediator of dispersal rates) and patch size, providing context for understanding the variability observed in dispersal effects among natural communities, as well as for developing conservation and management plans in an increasingly fragmented world.
个体在离散栖息地斑块间扩散的增加，应会使每个局部栖息地斑块中出现的物种平均数量增加。然而，实验研究发现扩散对局部物种丰富度的影响存在差异。优先效应、捕食者和栖息地异质性已被提出作为限制扩散对物种丰富度影响的机制。然而，栖息地斑块的大小可能会影响扩散如何调节能够持续存在的物种数量。我们研究了栖息地大小是否与扩散速率相互作用，从而影响局部栖息地中出现的物种数量。我们假设，扩散速率的增加对小栖息地中局部物种丰富度的积极影响要大于大栖息地，因为稀有物种将免受种群灭绝的影响。为了测试扩散速率与栖息地大小之间的相互作用，我们使用淡水浮游动物的模型群落，对实验池塘的大小和扩散速率进行了析因操作。我们发现，高扩散速率提高了小型实验池塘中的局部物种丰富度，但对大型实验池塘没有影响。我们的结果表明，在斑块连通性（扩散速率的一个介导因素）和斑块大小之间存在权衡，这为理解自然群落中扩散效应的变异性，以及在日益破碎化的世界中制定保护和管理计划提供了背景。
