Urbanization can affect arthropod abundance in different ways. While species with narrow habitat range and low dispersal ability often respond negatively to urban environments, many habitat generalist species with good dispersal ability reach high densities in city centers. This filtering effect of urban habitats can strongly influence predator-prey-mutualist interactions and may therefore affect the abundance of predatory and phytophagous species both directly and indirectly. Here, we assessed the effect of urbanization on aphids, predatory arthropods, and ants on field maple (Acer campestre) trees in and around the city of Budapest, Hungary. We used the percentage of impervious surfaces within a 500 m radius of each site as an index of the degree of urbanization. We found that the abundance of aphids increased with increasing level of urbanization. However, abundance of predatory arthropods and occurrence of poorly dispersing species within the predator community were negatively related to urbanization, and we identified these two independent factors as significant predictors of aphid abundances. The abundance of ants decreased with urbanization, and contrary to our expectations, did not affect the abundance pattern of aphids. Our results suggest that urbanization, by altering the abundance and composition of predator communities, can disrupt biological control of aphid populations, and thus may contribute to the aphid outbreaks on urban trees.

城市化可以不同方式影响节肢动物的数量。虽然生境范围狭窄且扩散能力低的物种通常会对城市环境产生负面影响，但许多具有良好扩散能力的生境通才物种在城市中心的密度很高。城市栖息地的这种过滤效果可以极大地影响食肉动物-食肉动物-相互之间的相互作用，因此可能直接或间接地影响捕食性和食植物性物种的丰富度。在这里，我们评估了城市化对蚜虫，掠食性节肢动物和蚂蚁对田野枫树（Acer campestre）匈牙利布达佩斯市及其周围的树木。我们将每个站点500 m半径内不透水表面的百分比用作城市化程度的指标。我们发现，随着城市化水平的提高，蚜虫的数量也增加了。然而，捕食性节肢动物的丰富和在捕食者群落中分散性差的物种的出现与城市化程度呈负相关，我们确定了这两个独立的因素是蚜虫数量的重要预测因子。蚂蚁的丰度随着城市化程度的降低而下降，这与我们的预期相反，并未影响蚜虫的丰度模式。我们的结果表明，城市化可以通过改变捕食者群落的数量和组成，破坏对蚜虫种群的生物控制，