Wild bees as pollinators of city trees

Abstract

Recent studies showed that diverse wild bee assemblages are more efficient pollinators than honeybees. In urban ecosystems pollination services are also important, for example for the reproduction of many plant species in parks, for the production of vegetables and fruits in home gardens, as well as other animals depending on bee‐pollinated plants. This study investigates the effect of ‘urbanity’ on the abundance, species richness and community structure of wild bees foraging at city trees and quantifies the contribution of wild bees and honeybees to successful pollination. Four common city tree species in Berlin, Germany, were sampled in three parks defined as ‘green spaces’ and compared with trees in more ‘urban areas’. In total, 57 wild bee species foraged at the observed trees representing 19 % of all known species in Berlin. Wild bee species richness showed only small differences between green spaces and urban areas even though social species were found more frequently in green areas. Wild bees visited flowers more frequently in green areas, whereas the numbers of honeybee flower visits were higher in urban areas. Wild bee but not honeybee flower visits showed a positive relationship with the reproductive success of trees. The results suggest that wild bees are important pollinators of city trees that dominate the pollinator community in green spaces. To support wild bee communities green spaces should be preserved and tree species with floral reward should be planted and preserved in urban areas.

Insights from measuring pollen deposition: quantifying the pre-eminence of bees as flower visitors and effective pollinators

“…Honeybees (Apis mellifera) were often the least effective type, though often the most abundant. This ties in with accumulating recent literature on the relative benefits of wild bees and of commercial honey bees, as pollinators of natural habitats and urban spaces (Lowenstein et al 2015;Hausmann et al 2016). Wild bees are also vital, and often better than Apis, as crop pollinators, with the importance of honeybees often over-emphasised in the past (see Breeze et al 2011;Garibaldi et al 2013).…”

Specialist nectar-yeasts decline with urbanization in Berlin

“…Again, this can be linked to effects on pollinators, as highly sealed areas provide lower food sources and are less attractive especially to wild bee pollinators22. Fewer nesting capabilities of soil inhabiting wild bees in these areas might lower pollinator species richness, and in turn decrease the dispersal rates of yeast species specialized in the floral niche.…”

Uptake and dissipation of neonicotinoid residues in nectar and foliage of systemically treated woody landscape plants

“…In urban areas, bees provide pollination services to community and residential gardens, to ornamental fruit-bearing trees and shrubs that feed birds and other desirable wildlife, and to many wild plant species [19][20][21][22][23][24][25]. Urban bee communities are dominated by polylectic species [19,20,[26][27][28] that collect nectar and pollen from diverse plants, including flowering trees and shrubs [29][30][31], so it is important that those floral resources not contain harmful levels of pesticide residues.…”