Bee community response to local and landscape factors along an urban-rural gradient

Abstract

Over a third of the world's crops require insect pollination, and reliance on pollination services for food continues to rise as human populations increase. Furthermore, as interest in urban agriculture has grown, so has a need for studies of urban pollinator ecology and pollination. Analyzing pollinator assemblages along a rural-urban gradient provides powerful mechanistic insight into how urbanization impacts pollinators. Yet, studies examining pollinators along urban-rural gradients are limited and results vary. Since pollinators vary tremendously in life history characteristics and respond to urbanization differently, studies from different regions would improve our understanding of pollinator response to urbanization. This study documents different bee assemblages along a high-plains semi-arid urban-rural gradient in Denver, Colorado, USA. Percent impervious surface was used to define the extent of urbanization at 12 sites and local and landscape characteristics were estimated using field assessments and geospatial analysis. Wild bees were collected and the relationships between urbanization and bee communities were explored using linear modeling. Overall, bee abundance and diversity decreased with increasing urbanization, suggesting that urban areas negatively impact bee communities. However, all bee guilds responded positively to local floral richness and negatively to the degree of landscape urbanization, suggesting that different types of bees responded similarly to urbanization. These findings suggest that providing a greater diversity of floral resources is key to mitigating the negative impacts of urbanization on pollinator communities.

Bees in the six: Determinants of bumblebee habitat quality in urban landscapes

“…Like the majority of bees found in cities (MacIvor et al, 2014;Matteson et al, 2008), B. impatiens is a diet generalist that is known to forage on a large number of plant species (Colla & Dumesh, 2010;Gervais et al, 2020;Vaudo et al, 2014), including many that attract other native pollinators. For for other bumblebee species (Jha & Kremen, 2013a,b) and native bee communities (Bennett & Lovell, 2019;Birdshire et al, 2020;Egerer et al, 2020;Fortel et al, 2014;Geslin et al, 2016). Similarly, functional green space in Toronto was associated with shorter foraging distances in our RDA analysis, which is consistent with previous research on the importance of forage for many other native bumblebees (Carvell et al, 2011(Carvell et al, , 2012(Carvell et al, , 2017Goulson et al, 2010;Redhead et al, 2016).…”

“…Impervious structures (e.g., roads, buildings, and other paved surfaces) had a clear negative impact on both B . impatiens ’ colony density and foraging distance in our analysis; similar detrimental effects of impervious surfaces have been documented for other bumblebee species (Jha & Kremen, 2013a , 2013b , 2013a , 2013b ) and native bee communities (Bennett & Lovell, 2019 ; Birdshire et al, 2020 ; Egerer et al, 2020 ; Fortel et al, 2014 ; Geslin et al, 2016 ). Similarly, functional green space in Toronto was associated with shorter foraging distances in our RDA analysis, which is consistent with previous research on the importance of forage for many other native bumblebees (Carvell et al, 2011 , 2012 , 2017 ; Goulson et al, 2010 ; Redhead et al, 2016 ).…”

“…Our high‐resolution analyses of the landscape features that enhance pollinator habitats in urban environments in Toronto are consistent with previous studies on bumblebees and other generalist native bees. Specifically, previous studies linked impervious paved surfaces and availability of forage as key negative and positive drivers, respectively, of habitat quality for native bee communities (Bennett & Lovell, 2019 ; Birdshire et al, 2020 ; Carvell et al, 2011 ; Egerer et al, 2020 ; Fortel et al, 2014 ; Geslin et al, 2016 ; Goulson et al, 2010 ; Jha & Kremen, 2013a , 2013b , 2013a , 2013b ).…”

Functional diversity of farmland bees across rural–urban landscapes in a tropical megacity

“…Some studies found that urban areas could be hotspots for bees (Baldock et al, 2015; Theodorou et al, 2020), but others found that they contributed to their decline (Bates et al, 2011; Geslin, Le Féon, et al, 2016; Pereira et al, 2021). Within urban areas, bee communities are affected by different biotic and abiotic drivers, such as urban warming and pollution (Hamblin et al, 2018) and other environmental factors ranging from local to landscape scales (Birdshire et al, 2020). Within their local habitats, flower cover and floral richness enhance their diversity (Bates et al, 2011; Hülsmann et al, 2015; Theodorou et al, 2017).…”

Insect-mediated pollination improves fruit quality of strawberries in an urban environment

“…These aspects of urban landscapes can allow cities to harbour diverse pollinator communities (Baldock et al 2015;Fortel et al 2014;Geslin et al 2015). Despite a growing interest in urban pollinator diversity (Banaszak-Cibicka et al 2018;Birdshire et al 2020) and pollination services (Harrison and Winfree 2015;Wenzel et al 2020), very few studies assess whether these unique urban pollinator communities can provide su cient pollination services to support urban crop production.…”