Data from: Dealing with mutualists and antagonists: specificity of plant-mediated interactions between herbivores and flower visitors, and consequences for plant fitness

1. Plants need to deal with antagonists, such as herbivores, while maintaining interactions with mutualists, such as pollinators that help plants to maximize their reproductive output. Although many plant species have inducible defences to save metabolic costs of defence in the absence of herbivores, plant responses induced by herbivore attack can have ecological costs. For example, herbivore-induced responses can affect flower traits and alter interactions with flower visitors. Such plant-mediated interactions between herbivores and flower visitors can affect plant reproductive output. Current knowledge on the generality and specificity of plant-mediated herbivore-flower-visitor interactions and its consequences for plant fitness is limited. 2. In this study, we investigated whether a broad range of herbivores feeding on the annual plant Brassica nigra affect interactions with flower visitors, whether the direction of interactions is predicted by the feeding modes (chewing and sap-feeding) and sites (above- and belowground) of the herbivores, and whether it results in fitness consequences for the plant. 3. Our results show that attack of B. nigra by a range of different herbivores influenced plant interactions with mutualist pollinators and an antagonist florivore, the pollen beetle Meligethes aeneus. Pollinator community composition was affected by herbivory, whereas overall pollinator attraction was maintained. Pollinator community composition of uninfested plants differed from that of chewing and root herbivore-infested plants. Main responders in the pollinator communities to changes induced by herbivory were syrphid flies, bumblebees, and solitary bees. Although the preference of pollen beetle adults was not affected by herbivory, beetle larvae performed best on plants infested with the nematode Heterodera schachtii. The changes in pollinator community composition and syrphid fly visitation can explain the observed increase in seed set of root herbivore-infested plants. 4. Interactions of flowering B. nigra plants with mutualist and antagonist insects are well integrated and conflicting interactions do not reduce reproductive output. Our results suggest some degree of specificity in herbivore-flower-visitor interactions with consequences for plant fitness. Specificity of plant responses were determined at the species level as well as the herbivore functional group level , and differed depending on the flower visitor. Because plant reproduction was affected by indirect plant-mediated interactions, these can potentially result in selection on plant strategies to optimize growth, defence, and reproduction.

1. 植物需要应对植食者（herbivores）等拮抗生物，同时维持与传粉者（pollinators）等互惠生物的互作——传粉者可帮助植物最大化生殖产出。尽管多数植物物种具备诱导防御机制，以在无植食者时节省防御代谢成本，但植食者攻击诱导的植物响应会带来生态成本。例如，植食者诱导的响应可影响花部性状，并改变与访花生物的互作。这类植食者与访花者之间的植物介导互作，会影响植物的生殖产出。目前学界对植物介导的植食者-访花者互作的普遍性与特异性，及其对植物适合度的影响的认知仍较为有限。
2. 本研究以一年生黑芥（Brassica nigra）为实验材料，探究了多类植食者取食是否会影响其与访花生物的互作；这类互作的方向是否可通过植食者的取食模式（咀嚼式与刺吸式）以及取食位点（地上与地下）进行预测；以及此类互作是否会为植物带来适合度层面的影响。
3. 研究结果显示，多类不同植食者对黑芥的取食，会影响植物与互惠型传粉者以及拮抗型花食者（florivore）——花粉甲虫（Meligethes aeneus）的互作。植食作用会改变传粉者群落组成，但整体传粉吸引力得以维持。未受侵染植株的传粉者群落组成，与受咀嚼式植食者以及根部植食者侵染的植株存在显著差异。传粉者群落中对植食诱导的变化响应最为显著的类群为食蚜蝇（syrphid flies）、熊蜂（bumblebees）与独居蜂（solitary bees）。尽管植食作用未影响花粉甲虫成虫的寄主偏好，但甲虫幼虫在被甜菜孢囊线虫（Heterodera schachtii）侵染的植株上生长表现最佳。传粉者群落组成的变化以及食蚜蝇的访花频次，可解释根部植食者侵染植株的结籽量提升现象。
4. 开花期黑芥植株与互惠型、拮抗型昆虫的互作整合度较高，且冲突性互作并不会降低植物的生殖产出。本研究结果表明，植食者-访花者互作存在一定程度的特异性，且该特异性会对植物适合度产生影响。植物响应的特异性可在物种水平以及植食者功能群水平得以体现，且随访花生物类群的不同而存在差异。由于植物生殖会受到间接植物介导互作的影响，此类互作可能会对植物优化生长、防御与生殖的策略产生选择压力。