CANCELLED - Restoration age increases plant-pollinator interactions and presence of specialists in urban meadows

Background/Question/Methods

Urbanization impacts biodiversity due to increases in habitat fragmentation, resource loss, and competition from introduced species. To support biodiversity and the ecosystem services it provides, much effort is now focused on measuring and mitigating the effects of urbanization. Wild bees (Hymenoptera: Apoidea) are one taxa of growing conservation concern as they provide essential pollination services. A common strategy to promote wild bee conservation is to augment flowering plant diversity through restoration and management of urban green spaces (UGS). We evaluate plant-pollinator interactions across urban meadow restorations varying in age, plant mix, and level of surrounding urban land cover to determine which factors are important in promoting the most interactions, as well as which bee species are most active, and which plant species are the most attractive. Over two summers (2020 and 2021), I evaluated plant-pollinator interactions across eleven sites in ‘The Meadoway’, a 16 km section of hydro-corridor in Toronto Canada, that is being converted from mown turf grass to urban meadows and other features to promote biodiversity and connecting people to nature. We used generalized linear mixed effects models to explore relationships between urban meadows and bee abundance, diversity, and interaction network properties.

Results/Conclusions

We observed a total of 1868 plant-pollinator interactions which included 29 bee genera and 68 flowering plant species. The most abundant bee genera in our surveys were Bombus (Apidae) (N = 911 interactions), Halictus (Halictidae) (N = 221), Melissodes (Apidae) (N = 114) and Agapostemon (Halictidae) (N = 108). All four genera were dominant across restoration year and ranked highest as generalist pollinators. The top three plants which received greatest visitation, were native/seeded False Sunflower (Heliopsis helianthoides: Asteraceae) (L.) (N = 254), Wild Bergamot (Monarda fistulosa: Lamiaceae) (L.) (N = 163), and spontaneous Birds Foot Trefoil, (Lotus corniculatus: Fabaceae) (L.) (N = 161). Top models revealed that restoration year was positively correlated with wild bee abundance and richness, and negatively correlated with evenness. Plant richness and urbanization were not significant for any of the variables measured, indicating the value of a continuous linear landscape. Overall, 7 specialist and cleptoparasite bee genera were found exclusively in restoration sites, highlighting the importance of matured restored meadows in urban areas. Additionally, non-native spontaneous plant species were attractive to bees in unrestored (98% of interactions) and newly restored (59% of interactions) sites, highlighting its contribution and consideration by practitioners aiming to conserve urban biodiversity.