Section of Ecology, Department of Biology, University of Turku, Turku, Finland.
Laboratory of Cell Cycles of Algae, Institute of Microbiology, Czech Academy of Sciences, Třeboň, Czech Republic.
Glob Chang Biol. 2017 Oct;23(10):4354-4364. doi: 10.1111/gcb.13692. Epub 2017 Apr 19.
Despite the increasing rate of urbanization, the consequences of this process on biotic interactions remain insufficiently studied. Our aims were to identify the general pattern of urbanization impact on background insect herbivory, to explore variations in this impact related to characteristics of both urban areas and insect-plant systems, and to uncover the factors governing urbanization impacts on insect herbivory. We compared the foliar damage inflicted on the most common trees by defoliating, leafmining and gall-forming insects in rural and urban habitats associated with 16 European cities. In two of these cities, we explored quality of birch foliage for herbivorous insects, mortality of leafmining insects due to predators and parasitoids and bird predation on artificial plasticine larvae. On average, the foliage losses to insects were 16.5% lower in urban than in rural habitats. The magnitude of the overall adverse effect of urbanization on herbivory was independent of the latitude of the locality and was similar in all 11 studied tree species, but increased with an increase in the size of the urban area: it was significant in large cities (city population 1-5 million) but not significant in medium-sized and small towns. Quality of birch foliage for herbivorous insects was slightly higher in urban habitats than in rural habitats. At the same time, leafminer mortality due to ants and birds and the bird attack intensity on dummy larvae were higher in large cities than in rural habitats, which at least partially explained the decline in insect herbivory observed in response to urbanization. Our findings underscore the importance of top-down forces in mediating impacts of urbanization on plant-feeding insects: factors favouring predators may override the positive effects of temperature elevation on insects and thus reduce plant damage.
尽管城市化的速度不断加快，但这一过程对生物相互作用的影响仍研究不足。我们的目的是确定城市化对背景昆虫取食的普遍影响模式，探索与城市地区和昆虫-植物系统特征相关的这种影响的变化，并揭示控制城市化对昆虫取食影响的因素。我们比较了 16 个欧洲城市相关的农村和城市生境中，食叶、潜叶和形成虫瘿的昆虫对最常见树木的叶片损伤。在其中两个城市，我们研究了桦树叶片对食草昆虫的质量、食叶昆虫因捕食者和寄生蜂而死亡的情况以及鸟类对人工塑料幼虫的捕食情况。平均而言，城市生境中昆虫对叶片的损失比农村生境低 16.5%。城市化对取食的整体不利影响的程度与地点的纬度无关，并且在所有 11 种研究的树种中相似，但随着城市面积的增加而增加：在大城市（城市人口 1-500 万）中显著，但在中、小城市中不显著。城市生境中桦树叶片对食草昆虫的质量略高于农村生境。同时，大型城市中蚂蚁和鸟类对潜叶虫的死亡率以及鸟类对假幼虫的攻击强度高于农村生境，这至少部分解释了观察到的城市化对昆虫取食的下降。我们的研究结果强调了在调节城市化对食草昆虫的影响方面，自上而下的力量的重要性：有利于捕食者的因素可能会抵消温度升高对昆虫的积极影响，从而减少植物损伤。
