Urbanization is a complex process associated with environmental changes affecting many biotic and abiotic ecosystem components, which cause the alteration of biological communities, habitat features, connectivity and stability. In particular, the urbanization process is usually associated with a decrease in species richness that parallels a general increase in the overall abundance of individuals, mostly due to generalist and tolerant species taking advantage of the altered environmental conditions and outcompeting and excluding native species. We here adopted a hierarchically nested sampling design to investigate the response of ground arthropods to the combined effects of multiple facets of urbanization, namely increased impervious surface cover, temperature and patch isolation, measured at small, intermediate and large spatial scale. We studied 15 plots of 150 m in diameter located in the city of Turin (NW-Italy), along an urbanization-cover gradient ranging from suburbia to the city center. For each plot we considered the level of urbanization at three different scales (circular buffers with a 100, 400 and 1600 m radius). Within each plot, we identified a control and an isolated subplot, and in each subplot, we measured ground temperature using dataloggers and we sampled ground arthropods with pitfall traps. Firstly, by relating ground temperature and urbanization cover, we showed that temperature values reflected an Urban Heat Island (UHI) effect, which indicates increasing values of temperature along the urbanization gradient. This trend was particularly evident at large scale regarding daily and diurnal temperature, and at small scale regarding nocturnal temperature. Secondly, we demonstrated that different groups of ground arthropods respond differently to urbanization cover, with major effects at the largest spatial scale. Finally, we extrapolated the differential contribution of urbanization cover, UHI-effect and patch isolation to the observed activity density of the investigated taxonomic groups: Coleoptera and Hemiptera were influenced by temperature, whereas Hymenoptera, Collembola, Acari and Araneae were mainly influenced by urbanization, especially in control subplots. Our results emphasize how a multitaxonomic approach can help unravel patterns of community assembly in urban areas.

中文翻译：

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城市化驱动因素对都灵市（意大利西北部）的节肢动物群落产生不同的影响

城市化是一个复杂的过程，与环境变化相关，影响着许多生物和非生物生态系统组成部分，导致生物群落，生境特征，连通性和稳定性发生变化。特别是，城市化进程通常与物种丰富度的下降相关，而物种丰富度的下降与个体总体丰度的总体上升相平行，这主要是由于通才和宽容的物种利用了变化的环境条件，竞争优势而将其排除在外而未包括在内。在这里，我们采用了分层嵌套的抽样设计，以研究地面节肢动物对城市化多个方面的综合影响的响应，即在小，中，大空间尺度上测量的不透水地表覆盖率，温度和斑块隔离度。我们研究了位于都灵市（意大利西北部）的15个直径为150 m的地块，沿郊区到市中心的城市化覆盖率梯度进行了研究。对于每个地块，我们考虑了三种不同规模的城市化水平（半径分别为100、400和1600 m的圆形缓冲区）。在每个图中，我们都确定了一个对照和一个隔离的子图，在每个子图中，我们使用数据记录仪测量了地温，并用陷阱陷阱对节肢动物进行了采样。首先，通过关联地面温度和城市化覆盖率，我们表明温度值反映了城市热岛效应，这表明温度随着城市化梯度的增加而增加。就日常和昼夜温度而言，这种趋势尤其明显，而对于夜间温度而言，这种趋势在小范围内尤其明显。其次，我们证明了不同种类的节肢动物对城市化覆盖的反应不同，在最大的空间尺度上产生了重大影响。最后，我们推断出城市化覆盖率，UHI效应和斑块隔离对所研究分类群观察到的活动密度的不同贡献：鞘翅目和半翅目受温度影响，而膜翅目，Collembola，Acari和Araneae主要受城市化影响，特别是在控制子图中。我们的研究结果强调了一种多分类方法如何能够帮助弄清城市地区的社区集会模式。我们推断出城市化覆盖率，UHI效应和斑块隔离对所研究分类群观察到的活动密度的不同贡献：鞘翅目和半翅目受温度影响，而膜翅目，Collembola，Acari和Araneae主要受城市化影响，特别是在控制子图。我们的研究结果强调了一种多分类方法如何能够帮助弄清城市地区的社区集会模式。我们推断出城市化覆盖率，UHI效应和斑块隔离对所研究分类群观察到的活动密度的不同贡献：鞘翅目和半翅目受温度影响，而膜翅目，Collembola，Acari和Araneae主要受城市化影响，特别是在控制子图。我们的研究结果强调了一种多分类方法如何能够帮助弄清城市地区的社区集会模式。