As fragmented landscapes become increasingly common around the world, managing the spatial arrangement of landscape elements (i.e., landscape configuration) may help to promote the conservation of biodiversity. However, the relative effects of landscape configuration on different dimensions of biodiversity across species assemblages are largely unknown. Thus, a key challenge consists in understanding when it is necessary to focus on landscape configuration, in addition to landscape composition, to achieve multifunctional landscapes. We tested the effects of landscape composition (the percentage of tree cover and built infrastructure) and landscape configuration (degree of fragmentation) on landscape-level species richness and different metrics of functional diversity of urban birds. We collected data on different bird guilds (nectarivores/frugivores, insectivores) from Brisbane, Australia. Using structural equation models, we found that landscape structure (landscape composition and configuration) affected functional diversity via two main pathways: (1) through effects of landscape composition, mediated by landscape configuration (indirect effects), and (2) through direct (“independent”) effects of landscape composition and configuration, filtering species with extreme trait values. Our results show that landscape-level species richness declined with the extent of built infrastructure, but patterns of trait diversity did not necessarily correlate with this variable. Landscape configuration had a stronger mediating effect on some metrics of the functional diversity of insectivores than on the functional diversity of frugivores/nectarivores. In addition, fragmentation increased the effects of built infrastructure for some traits (body size and dispersal capacity), but not for others (habitat plasticity and foraging behavior). These results suggest that differential approaches to managing landscape structure are needed depending on whether the focus is on protecting functional diversity or species richness and what the target guild is. Managing landscape fragmentation in areas with high levels of built infrastructure is important if the objective is to protect insectivore species with uncommon traits, even if it is not possible to preserve high levels of species richness. However, if the target is to enhance both functional diversity and species richness of multiple guilds, the focus should be on improving composition through the reduction of negative effects of built infrastructure, rather than promoting specific landscape configurations in growing cities.

中文翻译：

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解开景观结构对城市鸟类丰富度和功能多样性的直接和间接影响

随着碎片化景观在世界范围内变得越来越普遍，管理景观元素的空间排列（即景观配置）可能有助于促进生物多样性的保护。然而，景观配置对跨物种组合生物多样性不同维度的相对影响在很大程度上是未知的。因此，一个关键的挑战在于了解何时需要关注景观配置，除了景观构成，以实现多功能景观。我们测试了景观构成（树木覆盖率和已建成基础设施的百分比）和景观配​​置（破碎程度）对景观层面物种丰富度和城市鸟类功能多样性不同指标的影响。我们收集了来自澳大利亚布里斯班的不同鸟类行会（食蜜动物/食果动物、食虫动物）的数据。使用结构方程模型，我们发现景观结构（景观构成和配置）通过两个主要途径影响功能多样性：（1）通过景观构成的影响，由景观配置（间接影响）调节，和（2）通过直接（“独立”）景观构成和配置的影响，过滤具有极端特征值的物种。我们的结果表明，景观层面的物种丰富度随着基础设施建设的程度而下降，但性状多样性的模式并不一定与该变量相关。与食果动物/食蜜动物的功能多样性相比，景观配置对食虫动物功能多样性的某些指标具有更强的中介作用。此外，碎片化增加了建筑基础设施对某些特征（体型和传播能力）的影响，但对其他特征（栖息地可塑性和觅食行为）没有影响。这些结果表明，需要采用不同的方法来管理景观结构，具体取决于重点是保护功能多样性还是物种丰富度，以及目标群体是什么。如果目标是保护具有不常见特征的食虫物种，即使无法保持高水平的物种丰富度，管理基础设施水平高的地区的景观破碎化也很重要。然而，