Species‐specific responses to the environment can moderate the strength of interactions between plants, herbivores and parasitoids. However, the ways in which characteristics of plants, such as genotypic variation in herbivore induced volatiles (HIPVs) that attract parasitoids, affect trophic interactions in different contexts of plant patch size and plant neighbourhood is not well understood. We conducted a factorial field experiment with white cabbage Brassica oleracea accessions that differ in the attractiveness of their HIPVs for parasitoids, in the context of different patch sizes and presence or absence of surrounding Brassica nigra plants. Parasitism rates of experimentally introduced Pieris brassicae caterpillars and the presence of naturally occurring Pieris spp. caterpillars in the plots were assessed throughout the growing season. The abundance of Pieris caterpillars was neither affected by cabbage accession nor plot size. Later in the season, when B. nigra plants had senesced, fewer caterpillars were found on cabbage plants in plots with a B. nigra border. Parasitism rates fluctuated over the season, and were not affected by plot size. However, the B. nigra border negatively affected parasitism rates on the accession that is less attractive to the parasitoid Cotesia glomerata, but not on the more attractive accession. Our results show that plant variation in HIPVs can differentially influence herbivores and parasitoids depending on characteristics of the surrounding vegetation context. These findings underscore the importance of considering the interaction between focal plant traits and neighbourhood context to reliably predict trophic cascades.

中文翻译：

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空间尺度，邻近植物和植物挥发物的变化共同决定了宿主-寄生虫关系的强度

物种对环境的反应可以减轻植物，草食动物和寄生虫之间相互作用的强度。但是，人们对植物的特性（例如草食动物诱发的挥发物（HIPV）的基因型变异吸引寄生性寄生虫）在植物斑块大小和植物邻域的不同情况下影响营养相互作用的方式尚不甚了解。我们对白菜甘蓝种质进行了析因田间试验，在不同斑块大小以及周围是否存在黑芸苔植物的情况下，它们的HIPV对寄生虫的吸引力不同。实验引入菜青虫的寄生率毛毛虫和天然存在的Pieris spp。在整个生长季节对样地中的毛毛虫进行评估。菜青虫的丰度既不受卷心菜收成的影响，也不受地块大小的影响。在该季节的晚些时候，当黑芽孢杆菌植物衰老时，在带有黑芽孢杆菌边界的地块的卷心菜植物上发现的毛虫较少。寄生率随季节而波动，不受地块大小的影响。然而，黑带芽孢杆菌边界对该种的寄生率产生负面影响，而寄生虫对寄生小球藻的吸引力较小。，但在更具吸引力的加入上却没有。我们的结果表明，HIPV中的植物变异可根据周围植被环境的特征差异地影响草食动物和寄生虫。这些发现强调了考虑重点植物性状与邻域环境之间相互作用以可靠地预测营养级联的重要性。