Petermann Jana S, Kratina Pavel, Marino Nicholas A C, MacDonald A Andrew M, Srivastava Diane S
Institute of Biology, Freie Universität Berlin, Königin-Luise-Str. 1-3, D-14195, Berlin, Germany; Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), D-14195, Berlin, Germany; Department of Ecology and Evolution, University of Salzburg, Hellbrunnerstrasse 34, 5020, Salzburg, Austria.
School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, United Kingdom.
PLoS One. 2015 Mar 16;10(3):e0118952. doi: 10.1371/journal.pone.0118952. eCollection 2015.
Although stochastic and deterministic processes have been found to jointly shape structure of natural communities, the relative importance of both forces may vary across different environmental conditions and across levels of biological organization. We tested the effects of abiotic environmental conditions, altered trophic interactions and dispersal limitation on the structure of aquatic microfauna communities in Costa Rican tank bromeliads. Our approach combined natural gradients in environmental conditions with experimental manipulations of bottom-up interactions (resources), top-down interactions (predators) and dispersal at two spatial scales in the field. We found that resource addition strongly increased the abundance and reduced the richness of microfauna communities. Community composition shifted in a predictable way towards assemblages dominated by flagellates and ciliates but with lower abundance and richness of algae and amoebae. While all functional groups responded strongly and predictably to resource addition, similarity among communities at the species level decreased, suggesting a role of stochasticity in species-level assembly processes. Dispersal limitation did not affect the communities. Since our design excluded potential priority effects we can attribute the differences in community similarity to increased demographic stochasticity of resource-enriched communities related to erratic changes in population sizes of some species. In contrast to resources, predators and environmental conditions had negligible effects on community structure. Our results demonstrate that bromeliad microfauna communities are strongly controlled by bottom-up forces. They further suggest that the relative importance of stochasticity may change with productivity and with the organizational level at which communities are examined.
尽管随机过程和确定性过程共同塑造了自然群落的结构，但这两种力量的相对重要性可能因不同的环境条件和生物组织层次而异。我们测试了非生物环境条件、改变的营养相互作用和扩散限制对哥斯达黎加凤梨科植物水箱中水生微型动物群落结构的影响。我们的方法将环境条件的自然梯度与实地两个空间尺度上自下而上的相互作用（资源）、自上而下的相互作用（捕食者）和扩散的实验操作相结合。我们发现添加资源极大地增加了微型动物群落的丰度并降低了其丰富度。群落组成以可预测的方式向以鞭毛虫和纤毛虫为主的组合转变，但藻类和变形虫的丰度和丰富度较低。虽然所有功能组对添加资源都有强烈且可预测的反应，但物种水平上群落之间的相似性降低，这表明随机性在物种水平的组装过程中发挥了作用。扩散限制并未影响群落。由于我们的设计排除了潜在的优先效应，我们可以将群落相似性的差异归因于资源丰富的群落中与某些物种种群大小的不稳定变化相关的人口统计学随机性增加。与资源相反，捕食者和环境条件对群落结构的影响可忽略不计。我们的结果表明，凤梨科微型动物群落受到自下而上力量的强烈控制。它们还表明，随机性的相对重要性可能会随着生产力以及所研究群落的组织层次而变化。
