Supporting Bees in Cities: How Bees Are Influenced by Local and Landscape Features

Abstract

Urbanization is a major anthropogenic driver of decline for ecologically and economically important taxa including bees. Despite their generally negative impact on pollinators, cities can display a surprising degree of biodiversity compared to other landscapes. The pollinating communities found within these environments, however, tend to be filtered by interacting local and landscape features that comprise the urban matrix. Landscape and local features exert variable influence on pollinators within and across taxa, which ultimately affects community composition in such a way that contributes to functional trait homogenization and reduced phylogenetic diversity. Although previous results are not easily generalizable, bees and pollinators displaying functional trait characteristics such as polylectic diet, cavity-nesting behavior, and later emergence appear most abundant across different examined cities. To preserve particularly vulnerable species, most notably specialists that have become underrepresented within city communities, green spaces like parks and urban gardens have been examined as potential refuges. Such spaces are scattered across the urban matrix and vary in pollinator resource availability. Therefore, ensuring such spaces are optimized for pollinators is imperative. This review examines how urban features affect pollinators in addition to ways these green spaces can be manipulated to promote greater pollinator abundance and diversity.

A global review of urban pollinators and implications for maintaining pollination services in tropical cities

“…Another study carried out in Brazil demonstrated the importance of the urban environment in providing resources to small populations of the oil collecting bee Centris (Melacentris) collaris (Rocha-Filho et al 2018), indicating that some specialized floral resources may be found in urban environments and are essential for the maintenance of specialized bees. High floral abundance and diversity are the most important variables related to the maintenance of bees from different groups, offsetting the negative effects commonly associated with urbanization (Frankie et al 2013;Hülsmann et al 2015;Ayers and Rehan 2021). Such positive effects of floral resource availability have been described for cities in tropical countries such as Thailand (Tangtorwongsakul et al 2018;Stewart and Waitayachart 2020) and Costa Rica (Wojcik and McBride 2012), and is consistent with studies carried out in non-tropical regions (e.g., Ahrné et al 2009;Matteson and Langellotto 2010;Bates et al 2011;Hennig and Ghazoul 2011;Pardee and Philpott 2014;Hülsmann et al 2015).…”

Wild bee functional diversity and plant associations in native and conventional plant nurseries

“…We suspect the higher proportions of specialist bees at native nurseries are due in part to the presence of their corresponding native host plant species in native nurseries. Studies in other landscapes dominated by ornamental plants, such as urban areas, commonly detect fewer specialist bees when appropriate host plant taxa are lacking (Hernandez et al, 2009;Buchholz & Egerer, 2020;Ayers & Rehan, 2021). Indeed, we detected specialist bee species in the genera Diadasia, Micralictoides, and Ashmeadiella foraging on native ornamental cultivars belonging to their documented host families.…”

Nest aggregations of wild bees and apoid wasps in urban pavements: a “street life” to be promoted in urban planning

“…Hymenopteran communities also seem to be sensitive to landscape urban conversion (Buczkowski and Richmond 2012; Geslin et al 2016; Corcos et al 2019; Theodorou et al 2020a). The amount of floral resources becomes scarcer under the pressure of urban fragmentation but also with soil imperviousness due to increasing pavement that makes nesting sites inaccessible for ground-nesting Hymenopteran species (Burkman and Gardiner 2014; Harrison and Winfree 2015; Geslin et al 2016; Wenzel et al 2020; Ayers and Rehan 2021). Particularly, some research has shown a decrease in the richness of urban bee communities as well as a decrease in their size along an increasing urbanization gradient (Ahrné et al 2009; Fortel et al 2014; Eggenberger et al 2019).…”