The simplification and fragmentation of agricultural landscapes generate effects on insects at multiple spatial scales. As each functional group perceives and uses the habitat differently, the response of pest insects and their associated natural enemies to environmental changes varies. Therefore, landscape structure may have consequences on gene flow among pest populations in space. This study aimed to evaluate the effects of local and landscape factors, at multiple scales, on the local infestation, gene flow and broad dispersion dynamics of the pest insect Bemisia tabaci (Genn.) Middle East-Asia Minor 1 (MEAM-1, former biotype B) (Hemiptera: Aleyrodidae) and its associated natural enemies in a tropical agroecosystem. We evaluated the abundance of B. tabaci populations and their natural enemy community in 20 tomato farms in Brazil and the gene flow between farms from 2019 to 2021. Landscapes dominated by agriculture resulted in larger B. tabaci populations and higher gene flow, especially in conventional farms. A higher density of native vegetation patches disfavored pest populations, regardless of the management system. The results revealed that whitefly responds to intermediate spatial scales and that landscape factors interact with management systems to modulate whitefly populations on focal farms. Conversely, whitefly natural enemies benefited from higher amounts of natural vegetation at small spatial scales, while the connectivity between natural habitat patches was beneficial for natural enemies regardless of the distance from the focal farm. The resulting dispersion model predicts that the movement of whiteflies between farms increases as the amount of natural vegetation decreases. Our findings demonstrate that landscape features, notably landscape configuration, can mediate infestation episodes, as they affect pest insects and natural enemies in opposite ways. We also showed that landscape features interact with farm traits, which highlights the need for management strategies at multiple spatial scales. In conclusion, we demonstrated the importance of the conservation of natural areas as a key strategy for area-wide ecological pest management and the relevance of organic farming to benefit natural enemy communities in tropical agroecosystems.

中文翻译：

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自然栖息地的连通性和有机管理调节害虫传播、基因流动和天敌群落

农业景观的简化和破碎在多个空间尺度上对昆虫产生影响。由于每个功能群对栖息地的感知和利用不同，害虫及其相关天敌对环境变化的反应也不同。因此，景观结构可能会对太空害虫种群之间的基因流动产生影响。本研究旨在评估多尺度的当地和景观因素对害虫烟粉虱 ( Bemisia tabaci (Genn.) Middle East-Asia Minor 1 (MEAM-1，前生物型 B)（半翅目：粉虱科）及其在热带农业生态系统中的相关天敌。我们评估了 2019 年至 2021 年巴西 20 个番茄农场烟粉虱种群的丰度及其天敌群落以及农场之间的基因流。以农业为主的景观导致烟粉虱种群数量更大和基因流更高，特别是在传统农业中农场。无论管理系统如何，较高密度的本地植被斑块都不利于害虫种群。结果表明，粉虱对中间空间尺度有反应，景观因素与管理系统相互作用，以调节重点农场的粉虱种群。相反，粉虱天敌受益于小空间尺度上大量的自然植被，而自然栖息地斑块之间的连通性对天敌有利，无论距焦点农场的距​​离如何。由此产生的扩散模型预测，随着自然植被数量的减少，粉虱在农场之间的移动会增加。我们的研究结果表明，景观特征，特别是景观配置，可以调节侵扰事件，因为它们以相反的方式影响害虫和天敌。我们还表明，景观特征与农场特征相互作用，这凸显了在多个空间尺度上采取管理策略的必要性。总之，我们证明了自然区域保护作为全区域生态害虫管理关键战略的重要性，以及有机农业对热带农业生态系统中天敌群落的相关性。