Greenhouse crops are thought to be simplified ecosystems because they often consist of monocultures that are relatively isolated from their environment. However, insect pests are still able to colonize these protected crops, which threaten their yields. Similarly, natural enemies of pests may be able to colonize greenhouses, providing a form of natural biological pest control. Protected strawberry crops are grown in several types of greenhouses that vary in their degree of openness. Crops often suffer from aphid outbreaks, which can be partly controlled by insect parasitoids immigrating from the surrounding environment. We investigated variations over space and time in both the aphid and parasitoid community diversity and species assemblages associated with protected strawberry crops. We sampled aphids and parasitoids in five regions of France in the spring and summer of two successive years. Despite the relative isolation of these protected crops, we identified a high aphid species richness in them, even at the greenhouse scale. Aphid community composition varied with spatial and temporal factors, but the species assemblages present were mostly determined by local factors. Parasitoid communities were mostly similar among the studied regions, but varied between seasons, with this temporal variation being related to changes in aphid species composition. The study of trophic interactions occurring between aphids and parasitoids allowed the most prevalent and efficient parasitoid species to be identified. The structures of food webs strongly varied in time and space, compromising any prediction of “natural” biological control. We also highlighted ecological factors that can disrupt aphid biological control, such as the occurrence of hyperparasitism or the possibility of apparent mutualism between aphid species. Finally, we showed that the degree of openness of greenhouses influenced both the aphid communities and the hyperparasitism rates in them. These results provide valuable information to improve aphid biological control in protected crops.

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受保护作物中蚜虫和寄生虫的群落组成和营养网络的变化

温室作物被认为是简化的生态系统，因为它们通常由与环境相对隔离的单一栽培构成。但是，害虫仍然能够在这些受保护的作物上定殖，从而威胁其单产。同样，害虫的天敌可能能够在温室中定居，从而提供了自然生物害虫防治的一种形式。受保护的草莓作物种植在几种类型的温室中，这些温室的开放程度各不相同。农作物经常遭受蚜虫暴发，这可以部分地由从周围环境迁移的寄生虫来控制。我们调查了与保护性草莓作物有关的蚜虫和类寄生虫群落多样性以及物种组成随时间和空间的变化。连续两年的春季和夏季，我们在法国的五个地区取样了蚜虫和寄生虫。尽管这些受保护的农作物相对隔离，但即使在温室规模内，我们也发现其中有很高的蚜虫物种丰富度。蚜虫群落组成随时空因素而变化，但存在的物种组合主要由局部因素决定。在研究区域中，类寄生虫群落大部分相似，但是在季节之间变化，这种时间变化与蚜虫物种组成的变化有关。对发生在蚜虫和拟寄生虫之间的营养相互作用的研究使人们能够鉴定出最普遍和最有效的拟寄生虫物种。食物网的结构在时间和空间上变化很大，损害了对“自然”生物控制的任何预测。我们还重点介绍了可能破坏蚜虫生物控制的生态因素，例如高寄生病的发生或蚜虫物种之间明显的共生的可能性。最后，我们证明了温室的开放程度既影响了蚜虫群落，也影响了它们的超寄生率。这些结果提供了有价值的信息，以改善受保护作物中的蚜虫生物防治。