Interactive effects of productivity and predation on zooplankton diversity
Interactive effects of productivity and predation on zooplankton diversity
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DOI：
10.1111/oik.04099
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发表时间：
2017-11-01
期刊：
影响因子：
3.4
通讯作者：
Steiner, Christopher F.
中科院分区：
文献类型：
--
作者：
Asgari, Mitra;Steiner, Christopher F.
最近的研究表明，有必要了解捕食和生产力对物种共存和猎物多样性的交互影响。模型预测，如果较差的资源竞争者不太容易被捕食，并且如果生产力和/或捕食压力处于中等水平，则不同竞争能力的被捕食物种可以共存。因此，捕食者对猎物多样性的影响被预测为高度依赖于环境：从低到中等水平的生产力或捕食增加多样性，而在高水平的生产力或捕食时减少猎物的多样性。虽然已经有几项研究考察了食草性和生产力对初级生产者多样性的交互影响，但在捕食者-被捕食者系统中进行这种影响的实验研究很少。我们使用一个水生中游实验验证了这些预测，在这个实验中，我们操纵了浮游动物捕食性动物波纹藻的初始密度和生产力，以测试它们对周围池塘中常见的七种浮游动物、枝角类物种多样性的交互影响。两个生产力水平是通过磷的增加施加的，其水平与邻近天然池塘中的低水平和中等水平相当。我们使用开放系统来允许这种能够飞行的捕食者进行自然扩散和行为中介的数值反应。捕食者对浮游动物多样性的影响取决于生产力水平。在低生产力和高生产力条件下，捕食者物种丰富度呈下降趋势，而在高生产力条件下，猎物物种丰富度与捕食者密度呈单峰关系。当用Pielou的均匀指数或逆Simpson指数作为猎物多样性的衡量标准时，处理的效果较弱。我们的发现与模型预测基本一致，在模型预测中，捕食者可以在中等生产力和捕食强度水平上促进猎物共存和多样性。我们的工作还表明，猎物多样性和捕食强度之间的关系的函数形式可能是复杂的，并且高度依赖于环境背景。
Recent studies suggest the necessity of understanding the interactive effects of predation and productivity on species coexistence and prey diversity. Models predict that coexistence of prey species with different competitive abilities can be achieved if inferior resource competitors are less susceptible to predation and if productivity and/or predation pressure are at intermediate levels. Hence, predator effects on prey diversity are predicted to be highly context dependent: enhancing diversity from low to intermediate levels of productivity or predation and reducing diversity of prey at high levels of productivity or predation. While several studies have examined the interactive effects of herbivory and productivity on primary producer diversity, experimental studies of such effects in predator-prey systems are rare. We tested these predictions using an aquatic field mesocosm experiment in which initial density of the zooplankton predator Notonecta undulata and productivity were manipulated to test their interactive effects on diversity of seven zooplankton, cladoceran species that were common in surrounding ponds. Two productivity levels were imposed via phosphorus enrichment at levels comparable to low and intermediate levels found within neighboring natural ponds. We used open systems to allow for natural dispersal and behaviorally-mediated numerical responses by the flight-capable predator. Effects of predators on zooplankton diversity depended on productivity level. At low and high productivity, prey species richness declined while at high productivity it showed a unimodal relationship with increasing the predator density. Effects of treatments were weaker when using Pielou's evenness index or the inverse Simpson index as measures of prey diversity. Our findings are generally consistent with model predictions in which predators can facilitate prey coexistence and diversity at intermediate levels of productivity and predation intensity. Our work also shows that the functional form of the relationship between prey diversity and predation intensity can be complex and highly dependent on environmental context.