Drought events have the potential to mediate tri-trophic interactions. Changes in plant quality influence herbivore performance, which affects prey availability and quality for natural enemies. Parasitoid wasps are particularly vulnerable to these changes since their development is inextricably linked to that of their prey. However, we know little about the indirect effects of plant water limitation on parasitoid performance, especially the consequences of mild water limitation. This study investigated the ability of a parasitoid wasp (Aphidius colemani Viereck (Hymenoptera: Braconidae)) to suppress aphid (Rhopalosiphum padi L. (Hemiptera: Aphididae)) populations on well-watered, mildly stressed, or highly stressed wheat (Triticum aestivum L. (Poales: Poaceae)). We then investigated the role that aphid body size and behavioral interactions might play in wasp acceptance of aphid hosts. We found improved aphid suppression under mild and high-water limitation, but the underlying mechanisms were different. Mild-stress appeared to maximize parasitoid performance, as indicated by the highest mummy production. Aphids were larger when feeding on mildly stressed plants than on any other treatment, which suggests improved aphid quality for parasitoids. Improved aphid suppression under high-stress may have been driven by enhanced nonconsumptive effects. Despite improved aphid suppression, mummy formation was lowest on highly stressed plants. High-stress conditions have been shown to negatively affect aphid performance, so improved aphid suppression may be driven by poor aphid performance exacerbating the cost of interactions with parasitoids, such as stinging. No differences were observed in parasitoid foraging behaviors such as antennation or stinging across any treatments. This study highlights the importance of plant water stress intensity in affecting outcomes of parasitoid-host interactions.

中文翻译：

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植物胁迫对蚜虫-寄生虫相互作用的影响：干旱改善了蚜虫的抑制作用。

干旱事件可能会介导三营养相互作用。植物质量的变化会影响草食动物的表现，从而影响天敌的猎物供应和质量。寄生蜂特别容易受到这些变化的影响，因为它们的发育与猎物有着千丝万缕的联系。但是，我们对植物水分限制对寄生性行为的间接影响知之甚少，尤其是温和水分限制的后果。这项研究调查了在水分充足，轻度胁迫或高胁迫的小麦（Triticum aestivum L）上，拟寄生蜂（Aphidius colemani Viereck（Hymenoptera：Braconidae））抑制蚜虫（Rhopalosiphum padi L.（Hemiptera：Aphididae））种群的能力。 （波兰语：禾本科）。然后，我们调查了蚜虫的体型和行为相互作用可能在蚜虫寄主的黄蜂接受中发挥的作用。我们发现在温和高水限制下，蚜虫的抑制作用得到了改善，但其潜在机制却有所不同。如最高的木乃伊产量所表明的那样，轻度的压力似乎可以使拟寄生物的性能最大化。以轻度胁迫的植物为食时，蚜虫比其他任何处理方法都大，这表明改善了寄生虫的蚜虫质量。增强的非消费效应可能推动了高胁迫下蚜虫抑制能力的提高。尽管改善了蚜虫抑制作用，但在高胁迫下的植物中木乃伊的形成最低。高压力条件已被证明会对蚜虫的性能产生负面影响，因此，改善的蚜虫抑制作用可能是由不良的蚜虫性能所驱动，加剧了与寄生虫相互作用（例如刺痛）的成本。在任何处理中，未观察到类寄生物觅食行为（如触角或刺痛）的差异。这项研究强调了植物水分胁迫强度在影响寄生虫-宿主相互作用的结果中的重要性。