As the world becomes more and more urbanized, it is increasingly important to understand the impacts of urban landscapes on biodiversity. Urbanization can change local habitat factors and decrease connectivity among local habitats, with major impacts on the structure of natural food webs. However, most studies have focused on single species, or compared rural to urban habitats, which do not inform us on how to design and manage cities to optimize biodiversity. To understand the local and spatial drivers of ecological communities within urban landscapes, we assessed the relative impact of local habitat factors (sunlight exposure and leaf litter) and spatial connectivity on an oak-associated herbivore community within an urban landscape. From the local habitat factors, leaf litter but not sunlight exposure was related to herbivore species richness, with leaf litter contributing to the maintenance of high species richness on isolated trees. Guilds and species differed strongly in their response to local habitat factors and connectivity, resulting in predictable variation in insect community composition among urban oaks. Taken together, our study shows an interactive effect of local and spatial factors on species richness and species composition within an urban context, with guild- and species-specific life histories determining the response of insects to urban landscapes. To maintain biodiversity in the urban landscape, preserving a dense network of local habitats is essential. Moreover, allowing leaf litter to accumulate can be a simple, cost-effective conservation management practice.

Observational field study on the galling and leafmining insects on oak trees in Stockholm, Sweden.

Data contains the abundances of leaf mining and galling species on each tree (84 trees), as well as the free-feeding herbivory scored for each tree (presence absence of free feeding herbivory on 25 leaves per tree).

Data processed in R, version 3.6.3.

For methodological details, see Barr et al. 2021, https://www.sciencedirect.com/science/article/pii/S0169204621001407.