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-寄生蜂相互作用的影响：干旱提高了蚜虫的抑制作用

干旱事件有可能调解三营养相互作用。植物质量的变化会影响食草动物的表现，从而影响天敌的猎物可用性和质量。寄生蜂特别容易受到这些变化的影响，因为它们的发育与其猎物的发育密不可分。然而，我们对植物水分限制对寄生蜂性能的间接影响知之甚少，尤其是轻度限制水分的后果。本研究调查了寄生蜂 (Aphidius colemani Viereck (Hymenoptera: Braconidae)) 抑制蚜虫 (Rhopalosiphum padi L. (Hemiptera: Aphididae)) 种群对水分充足、轻度胁迫或高度胁迫的小麦 (Triticum aestivum L. . (Poales: 禾本科))。然后，我们研究了蚜虫体型和行为相互作用在黄蜂接受蚜虫宿主中可能发挥的作用。我们发现在轻度和高水限制下改善了蚜虫抑制，但潜在的机制不同。正如最高的木乃伊产量所表明的那样，轻微的压力似乎可以最大限度地提高寄生蜂的性能。以轻度胁迫植物为食的蚜虫比任何其他处理方法都大，这表明寄生蜂的蚜虫质量有所提高。在高压力下改进的蚜虫抑制可能是由增强的非消耗效应驱动的。尽管对蚜虫的抑制有所改善，但在高度胁迫的植物上木乃伊的形成是最低的。高压力条件已被证明会对蚜虫的性能产生负面影响，因此，改进的蚜虫抑制可能是由于蚜虫表现不佳，加剧了与寄生蜂相互作用的成本，例如刺痛。在任何处理中未观察到寄生蜂觅食行为（例如触角或刺痛）的差异。这项研究强调了植物水分胁迫强度在影响寄生蜂-宿主相互作用结果中的重要性。