Using an ecosystem-level manipulation to understand host-parasite interactions and how they vary with study venue
Using an ecosystem-level manipulation to understand host-parasite interactions and how they vary with study venue
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使用生态系统层面的操作来了解宿主与寄生虫的相互作用以及它们如何随研究地点而变化
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发表时间：
2012
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通讯作者：
Pieter T. J. Johnson
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作者：
Kevin B. Lunde;V. Resh;Pieter T. J. Johnson
我们使用分层方法，包括多年的区域实地调查、重复的池塘围栏以及未重复的寄生虫感染生态系统操纵，研究了剧毒吸虫Ribeiroia ondatrae（这种吸虫与美国各地的两栖动物畸形有关）与其两栖动物宿主（Pseudacris regilla）之间的相互作用。这种多层次方法的结果提供了感染与畸形之间因果关系的有力证据，同时提供了有关实验场地对效应大小影响的更多见解。在加州北部 18 个湿地的年份中，Ribeiroia 感染是畸形频率的有力预测因子，所有地点的畸形频率范围为 0% 至 77%（n = 6,511）。相应地，使用为期三年的控制前后影响（BACI）设计将超过 500 只受 Ribeiroia 感染的蜗牛添加到实验划分的湿地中，导致在操纵年期间（但不是操纵前或操纵后）Ribeiroia 感染急剧增加和 P. regilla 严重畸形。这些结果得到了在分割湿地（Hog Lake）两侧进行的重复（n = 16）围栏/隔离研究的结果的补充，该研究表明，仅在允许寄生虫进入的笼子内的幼虫中以及仅在被操纵的一侧中，感染和畸形增加。没有观察到动物死亡率因笼子类型而存在差异。观察到的感染和畸形之间的斜率作为场地的函数（之前的实验室工作和本研究的两个空间尺度（笼子和整个池塘））的比较表明，小规模实验相对于较大空间范围的结果表现出更强的影响。多年抽样还表明，畸形青蛙不太可能在成年后返回，这凸显了与高 Ribeiroia 感染相关的种群水平影响的可能性。总而言之，这些结果为现实条件下 Ribeiroia 感染与两栖动物畸形之间的因果关系提供了支持，同时强调了研究地点对这种关系强度的影响。
We investigated interactions between the virulent trematode Ribeiroia ondatrae, which has been linked to amphibian malformations across the United States, and its amphibian host (Pseudacris regilla) using a hierarchical approach involving multi-year regional field surveys, replicated pond enclosures, and an unreplicated ecosystem manipulation of parasite infection. Results of this multi-tiered approach provide strong evidence of the causal linkage between infection and malformations while offering additional insights about the influence of experimental venue on effect size. Among years and across 18 wetlands in northern California, Ribeiroia infection was a strong predictor of malformation frequency, which ranged from 0 to 77% at all sites (n = 6,511). Correspondingly, the addition of >500 Ribeiroia infected snails to an experimentally divided wetland using a three-year Before After Control Impact (BACI) design caused sharp increases in Ribeiroia infection and severe malformations in P. regilla during the manipulation year (but not pre- or post-manipulation). These results were complemented by the findings from a replicated (n = 16) enclosure/exclosure study conducted on both sides of the divided wetland (Hog Lake), which showed increased infection and malformations only among larvae within cages that allowed parasite entry and only on the manipulated side. No differences in mortality were observed among animals as a function of cage type. A comparison of the slope between observed infection and malformations as a function of venue (previous laboratory work and the two spatial scales of this study (cages and whole-pond)) indicated that small-scale experiments exhibit stronger effects relative to results from larger spatial extents. Multi-year sampling also indicated that malformed frogs were unlikely to return as breeding adults, highlighting the potential for population-level impacts associated with high Ribeiroia infections. Taken together, these results provide support for the causal relationship between Ribeiroia infection and amphibian malformations under realistic conditions while simultaneously emphasizing the influence of study venue on the strength of this relationship.