1. The scope and complexity of interactions within community food webs necessitates their simplification to a community module scale for conducting empirical studies. An outdoor mesocosm study in the USA quantified the strengths of direct and indirect interactions between two herbivore congeners that fed on two aquatic plant species while sharing a parasitoid.
2. Kalopolynema ema (Hymenoptera: Mymaridae) is a stenophagous native egg parasitoid that attacks the hemipteran species in this study, Megamelus davisi (Hemiptera: Delphacidae), a native herbivore that feeds on the native aquatic species Nuphar advena, and the introduced biological control agent Megamelus scutellaris (Hemiptera: Delphacidae) that feeds on the non‐native aquatic species waterhyacinth, Pontederia crassipes.
3. The presence of M. scutellaris did not significantly increase parasitism of M. davisi indicating that apparent competition was not a factor in this community module. There was no evidence of any trophic cascades caused by these interactions based on the relative growth rates of biomass and leaf area for both plant species.
4. Synthesis and applications. The relative strengths of community interactions varied with herbivore densities suggesting that should negative indirect effects with biological control agents occur they would likely be transient and closely linked to population dynamics as influenced by abiotic factors like temperature. Despite identifying potential negative interactions using path analysis, we saw no apparent competition following the insertion of a weed biological control agent into a community that contains an ecological analog. In this example, the primary negative interaction was biotic resistance to Megamelus scutellaris from attack by Kalopolynema ema. Adopting weed management tactics that emphasize efficacy, sustainability and environmental benevolence argue for the use of classical biological control when appropriate.

中文翻译：

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经典的生物防治和明显的竞争：评估凤眼兰入侵的社区模块

1. 社区食物网中互动的范围和复杂性使其必须简化为进行实证研究的社区模块规模。在美国进行的一项室外中观研究，量化了以两种水生植物物种为食同时共享寄生虫的两种草食动物同系物之间直接和间接相互作用的强度。
2. Kalopolynema ema（Hymenoptera：Mymaridae）是一种食虫性的原生卵寄生虫，它攻击半翅目物种，该物种是Megamelus davisi（Hemiptera：Delphacidae），它是一种以天然水生动物Nuphar advena为食的原生草食动物，还引入了生物防治剂Megamelus。 scutellaris（半翅目：飞虱科）是对非本地水产品种饲料水葫芦，梭鱼草属葫芦。
3. 黄cut分枝杆菌的存在并没有显着增加戴维斯分枝杆菌的寄生性，这表明明显的竞争并不是该社区模块的一个因素。根据两种植物的生物量和叶面积的相对生长速率，没有证据表明这些相互作用引起营养级联反应。
4. 综合与应用。群落相互作用的相对强度随草食动物密度的变化而变化，这表明如果发生与生物防治剂的负面间接影响，它们很可能是短暂的，并与受温度等非生物因素影响的种群动态密切相关。尽管使用路径分析确定了潜在的负面相互作用，但在将杂草生物防治剂插入包含生态类似物的社区后，我们没有看到明显的竞争。在这个例子中，主要的负性相互作用是对来自Kalopolynema ema的攻击的黄MegaMegamelus scutellaris的生物抗性。采用强调功效，可持续性和环境仁慈的杂草治理策略，主张在适当的时候使用经典的生物防治方法。