Data from: Habitat connectivity and local conditions shape taxonomic and functional diversity of arthropods on green roofs

Summary 1. Increasing development of urban environments creates high
pressure on green spaces with potential negative impacts on biodiversity
and ecosystem services. There is growing evidence that green roofs –
rooftops covered with vegetation – can contribute mitigate the loss of
urban green spaces by providing new habitats for numerous arthropod
species. 2. Whether green roofs can contribute to enhance taxonomic and
functional diversity and increase connectivity across urbanized areas
remains, however, largely unknown. Furthermore, only limited information
is available on how environmental conditions shape green roof arthropod
communities. 3. We investigated the community composition of arthropods
(Apidae, Curculionidae, Araneae and Carabidae) on 40 green roofs and 40
green sites at ground level in the city of Zurich, Switzerland. We
assessed how the site's environmental variables (such as area,
height, vegetation, substrate and connectivity among sites) affect species
richness and functional diversity using generalized linear models. We used
an extension of co-inertia analysis (RLQ) and fourth-corner analysis to
highlight the mechanism underlying community assemblages across taxonomic
groups on green roof and ground communities. 4. Species richness was
higher at ground-level sites, while no difference in functional diversity
was found between green roofs and ground sites. Green roof arthropod
diversity increased with higher connectivity and plant species richness,
irrespective of substrate depth, height and area of green roofs. The
species trait analysis reviewed the mechanisms related to the
environmental predictors that shape the species assemblages of the
different taxa at ground and roof sites. 5. Our study shows the important
contribution of green roofs in maintaining high functional diversity of
arthropod communities across different taxonomic groups, despite their
lower species richness compared to ground sites. Species communities on
green roofs revealed to be characterized by specific trait assemblages.
The study also provides details on the environmental conditions that
influence arthropod diversity and gives new perspectives on how the design
of green roofs can be improved to increase their ecological value.
Furthermore, the study highlights the importance of integrating green
roofs in planning policies which aim to enhance urban habitat
connectivity.