Urban and forest trees provide valuable ecosystem services. However, they are increasingly threatened by invasive forest pests and pathogens. Trees in urban areas are often the first potential hosts non-native tree-feeding insects and tree pathogens (“pests”) encounter after introduction in a novel region. If the trees encountered are suitable hosts, these pests can establish and become invasive – eventually also in surrounding forests. Here, we compared tree species and genus composition between urban areas and surrounding forests and examined the implications for host availability for forest pests and potential effects on invasibility. We compiled and standardised 26 urban tree inventories, containing ∼ 500.000 individual trees. We used multivariate analyses to compare urban tree composition with forest tree composition from forests surrounding each municipality (10 km radius), derived from the Swiss National Forest Inventory. With > 1300 different tree species, species richness of urban trees was 17 times higher than species richness in surrounding forests. Linear models and multivariate analyses revealed that host availability for forest quarantine pests is significantly higher in urban areas than in forests, with large differences in host suitability for different quarantine pests between urban and forest tree assemblages. This indicates that differences in species composition in urban and forest trees can result in increased host availability, possibly facilitating the establishment of quarantine forest pests.

中文翻译：

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城市地区树种丰富度和多样性高于森林：对入侵树木害虫和病原体宿主可用性的影响


城市和森林树木提供了宝贵的生态系统服务。然而，它们日益受到入侵性森林害虫和病原体的威胁。城市地区的树木通常是非本地食树昆虫和树木病原体（“害虫”）引入新地区后遇到的第一个潜在宿主。如果遇到的树木是合适的宿主，这些害虫就会定居并变得具有入侵性——最终也会侵入周围的森林。在这里，我们比较了城市地区和周围森林之间的树种和属组成，并研究了对森林害虫宿主可用性的影响以及对入侵的潜在影响。我们编制并标准化了 26 个城市树木清单，其中包含约 500,000 棵树木。我们使用多变量分析来比较城市树木组成与来自瑞士国家森林清单的每个城市周围（半径 10 公里）森林的森林树木组成。城市树木有超过 1300 种不同的树种，其物种丰富度是周围森林的物种丰富度的 17 倍。线性模型和多变量分析表明，城市地区森林检疫性有害生物的寄主可用性显着高于森林，城市和森林树木组合对不同检疫性有害生物的寄主适宜性存在较大差异。这表明城市和森林树木物种组成的差异可能导致宿主可用性增加，可能促进检疫性森林害虫的建立。