Friendly competition: evidence for a dilution effect among competitors in a planktonic host-parasite system
Friendly competition: evidence for a dilution effect among competitors in a planktonic host-parasite system
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DOI：
10.1890/08-0838.1
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发表时间：
2009-03-01
期刊：
影响因子：
4.8
通讯作者：
Caceres, Carla E.
中科院分区：
文献类型：
--
作者：
Hall, Spencer R.;Becker, Claes R.;Caceres, Carla E.
疾病生态学中的“稀释效应”概念提供了一种有趣的可能性，即巧妙地操纵能力较弱的宿主可以降低能力较强的宿主群体中的疾病流行率。基本概念很简单：宿主物种对寄生虫的适应性（能力）各不相同，当有更多不称职的宿主与媒介相互作用或消除寄生虫的自由生活阶段时，疾病传播就会减少。然而，宿主物种之间也经常以其他生态方式相互作用，如：例如，在一个实施例中，资源的竞争者。这些同时发生的多重相互作用（疾病稀释和资源竞争）的最终结果很难预测。尽管如此，我们还是看到了这两种角色在寄生宿主-寄生虫系统中同时运作的特征。我们记录了美国中西部一种有毒真菌（Metschnikowia bicuspidata）流行规模的明显时空变化。S.湖泊种群的一个占主导地位的甲壳类食草动物（Daphnia dentifera）。我们发现，这种变化被捕获的水蚤组合结构的变化。具有较小流行的湖泊年的特征是由不太合适的宿主（"稀释剂"，D。pulicaria和D. retrocurva，其适用性是在实验室实验和实地调查中确定的）。此外，在一个季节内，随着流行病的减少，不太合适的宿主增加。这些观察结果与稀释效应一致。然而，更详细的时间序列分析（使用多变量自回归模型）的三个密集采样的流行病显示这些水蚤物种之间的稀释和资源竞争之间可能的相互作用的签名。这种相互作用的净结果可能促进了这些真菌爆发的终止。在稀释型宿主与更有能力的宿主竞争的"友好竞争"系统中，这种结果是否总是会出现？这个问题的答案在疾病生态学的前沿。
The "dilution effect'' concept in disease ecology offers the intriguing possibility that clever manipulation of less competent hosts could reduce disease prevalence in populations of more competent hosts. The basic concept is straightforward: host species vary in suitability ( competence) for parasites, and disease transmission decreases when there are more incompetent hosts interacting with vectors or removing free-living stages of a parasite. However, host species also often interact with each other in other ecological ways, e. g., as competitors for resources. The net result of these simultaneous, multiple interactions ( disease dilution and resource competition) is challenging to predict. Nonetheless, we see the signature of both roles operating concurrently in a planktonic host-parasite system. We document pronounced spatiotemporal variation in the size of epidemics of a virulent fungus (Metschnikowia bicuspidata) in Midwestern U. S. lake populations of a dominant crustacean grazer ( Daphnia dentifera). We show that some of this variation is captured by changes in structure of Daphnia assemblages. Lake-years with smaller epidemics were characterized by assemblages dominated by less suitable hosts ("diluters,'' D. pulicaria and D. retrocurva, whose suitabilties were determined in lab experiments and field surveys) at the start of epidemics. Furthermore, within a season, less suitable hosts increased as epidemics declined. These observations are consistent with a dilution effect. However, more detailed time series analysis ( using multivariate autoregressive models) of three intensively sampled epidemics show the signature of a likely interaction between dilution and resource competition between these Daphnia species. The net outcome of this interaction likely promoted termination of these fungal outbreaks. Should this outcome always arise in "friendly competition'' systems where diluting hosts compete with more competent hosts? The answers to this question lie at a frontier of disease ecology.