Rich pollinator assemblages are documented in some cities despite habitat fragmentation and degradation, suggesting that urban areas have potential as pollinator refuges. To inform urban bee conservation, we assessed local‐ and landscape‐scale drivers of bee community composition and foraging within vacant lots of Cleveland, Ohio, USA. Cleveland is a shrinking city, a type of urban area that has an over‐abundance of vacated greenspaces as a result of population loss and subsequent demolition of abandoned infrastructure. As such, Cleveland represents over 350 post‐industrial cities worldwide that are all promising locations for bee conservation. Across a network of 56 residential vacant lots (each ~30 m × 12 m), we established seven unique habitats, including seeded native prairies, to investigate how vegetation management and landscape context at a 1,500 m radius influenced urban bee communities. We assessed the distribution of several bee functional traits, diversity and abundance with pan and malaise traps. Foraging frequency was determined with plant–pollinator interaction networks derived from vacuum collections of bees at flowers. We observed higher bee richness and increased abundance of smaller sized bees as the size of surrounding greenspace patches increased within a 1,500 m radius landscape buffer. Within habitats, seeded treatments had no effect on bees but greater plant biomass and shorter vegetation were correlated with increased bee richness and abundance. Plant–pollinator interaction networks were dominated by spontaneous non‐native vegetation, illustrating that this forage supports urban bees.
There is concern that urbanization threatens bees, a diverse group of economic importance. The impact of urbanization on bees is likely mediated by their phenotypic traits.
We examine how urban cover and resource availability at local and landscape scales influences both species taxonomic and functional diversity in bees.
We used a combination of aerial netting and pan traps across six sampling periods to collect wild bees in 18 urban gardens spanning more than 125 km of the California central coast. We identified 3537 specimens to genus and, when possible, to species to obtain species richness and abundance at each site. For each species we measured a suite of bee traits, including body size, sociality, nesting location, nesting behavior, pollen-carrying structure, parasitism, and lecty.
We found that increased garden size was positively associated with bee species richness and abundance. Somewhat counterintuitively, we found that urban cover surrounding gardens (2 km) was positively associated with bee species richness. Urban cover was also associated with the prevalence of certain bee traits, such as bees that excavate nests over those who rent, and bees with non-corbiculate structures. We suggest that urban habitats such as gardens can host a high number of bee species, but urbanization selects for species with specific traits.
These findings illustrate that local and landscape features both influence bee abundance, species richness, and the frequency of specific traits. We highlight the importance of trait-based approaches for assessing biodiversity in urban landscapes, and suggest conceptualizing urbanization as a process of habitat change rather than habitat loss.
- NSF-PAR ID:
- 10362916
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Landscape Ecology
- Volume:
- 37
- Issue:
- 2
- ISSN:
- 0921-2973
- Format(s):
- Medium: X Size: p. 583-599
- Size(s):
- ["p. 583-599"]
- Sponsoring Org:
- National Science Foundation
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