Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
Exp Appl Acarol. 2011 Apr;53(4):311-22. doi: 10.1007/s10493-010-9410-8. Epub 2010 Nov 5.
Population dynamics models suggest that both the over-all level of resource productivity and spatial variability in productivity can play important roles in community dynamics. Higher productivity environments are predicted to destabilize consumer-resource dynamics. Conversely, greater heterogeneity in resource productivity is expected to contribute to stability. Yet the importance of these two factors for the dynamics of arthropod communities has been largely overlooked. I manipulated nutrient availability for strawberry plants in a multi-patch experiment, and measured effects of overall plant quality and heterogeneity in plant quality on the stability of interactions between the phytophagous mite Tetranychus urticae and its predator Phytoseiulus persimilis. Plant size, leaf N content and T. urticae population growth increased monotonically with increasing soil nitrogen availability. This gradient in plant quality affected two correlates of mite population stability, population variability over time (i.e., coefficient of variation) and population persistence (i.e., proportion of plant patches colonized). However, the highest level of plant quality did not produce the least stable dynamics, which is inconsistent with the "paradox of enrichment". Heterogeneity in plant productivity had modest effects on stability, with the only significant difference being less variable T. urticae densities in the heterogeneous compared to the corresponding homogeneous treatment. These results are generally congruent with metapopulation theory and other models for spatially segregated populations, which predict that stability should be governed largely by relative movement rates of predators and prey--rather than patch quality.
种群动态模型表明,资源生产力的总体水平和生产力的空间变异性都可以在群落动态中发挥重要作用。更高生产力的环境预计会使消费者-资源动态不稳定。相反,资源生产力的更大异质性预计会有助于稳定。然而,这两个因素对节肢动物群落动态的重要性在很大程度上被忽视了。我在一个多斑块实验中操纵了草莓植物的养分可用性,并测量了植物整体质量和植物质量异质性对植食性螨 Tetranychus urticae 与其捕食者 Phytoseiulus persimilis 之间相互作用稳定性的影响。植物大小、叶片氮含量和 T. urticae 种群增长率随土壤氮供应的增加而单调增加。这种植物质量梯度影响了螨种群稳定性的两个相关指标,即随时间变化的种群变异性(即变异系数)和种群持久性(即被植物斑块定殖的比例)。然而,最高水平的植物质量并没有产生最不稳定的动态,这与“富营养化悖论”不一致。植物生产力的异质性对稳定性有适度的影响,唯一显著的差异是在异质处理中,T. urticae 密度的变异性比相应的同质处理小。这些结果与集合种群理论和其他空间分离种群模型基本一致,这些模型预测稳定性主要由捕食者和猎物的相对迁移率决定,而不是由斑块质量决定。