1. Density‐ and trait‐mediated indirect interactions (DMIIs and TMIIs respectively) are important drivers of community dynamics but how plant nutrients (bottom‐up effects) affect the magnitude of such indirect interactions has been scarcely addressed.
2. To assess the impact of bottom‐up forces on indirect interactions, we carried out laboratory and greenhouse experiments manipulating plant nutrient supplies in a four‐species diamond food web consisting of a plant (tomato), two phytophagous insects (a leafminer and an aphid) and a predator (a mirid bug) attacking both herbivores.
3. Multiple negative indirect effects of the leafminer occurred towards the aphid. The presence of its eggs negatively affected aphid population growth through increased predator abundance (DMIIs), and larval herbivory slowed down aphid development and negatively modulated aphid behaviours, for example they spent less time feeding (TMIIs), likely owing to enhanced plant chemical defences and/or decreased plant nutritional quality. Moreover, the low plant nutrient supply further magnified TMIIs.
4. Synthesis . Abiotic factors modulated predator‐ and plant‐mediated indirect interactions among herbivorous community members. Our study highlights the importance of using a holistic approach, from foliar chemistry to community dynamics, for disentangling interspecific interactions in a simple food web.

中文翻译：

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植物营养供应改变了昆虫食草动物之间间接相互作用的程度：从叶化学到群落动态

1. 密度和性状介导的间接相互作用（分别为DMII和TMII）是群落动态的重要驱动力，但几乎没有解决植物养分（自下而上的影响）如何影响这种间接相互作用的程度。
2. 为了评估自下而上的作用力对间接相互作用的影响，我们进行了实验室和温室实验，在由植物（番茄），两种植物吞噬性昆虫（食叶虫和蚜虫）组成的四类钻石食物网中操纵植物的营养供应。和一个捕食者（一种金龟子）攻击这两个草食动物。
3. 采叶机对蚜虫产生了多种负面的间接影响。它的卵的存在通过增加捕食者的丰度（DMIIs）对蚜虫种群的生长产生不利影响，而幼虫草食放慢了蚜虫的发育并对蚜虫的行为产生了负面的影响，例如，它们花了更少的时间进食（TMIIs），这可能是由于植物化学防御能力的增强和/或植物营养品质下降。此外，植物养分供应不足使TMII进一步放大。
4. 综合。非生物因子调节食草动物群落成员之间的捕食者和植物介导的间接相互作用。我们的研究强调了使用从叶化学到群落动力学的整体方法来区分简单食物网中种间相互作用的重要性。