Urbanization is one of the major anthropogenic processes contributing to local habitat loss and extirpation of numerous species, including wild bees, the most widespread pollinators. Little is known about the mechanisms through which urbanization impacts wild bee communities, or the types of urban green spaces that best promote their conservation in cities. The main objective of this study was to describe and compare wild bee community diversity, structure, and dynamics in two Canadian cities, Montreal and Quebec City. A second objective was to compare functional trait diversity among three habitat types (cemeteries, community gardens and urban parks) within each city. Bees were collected using pan traps and netting on the same 46 sites, multiple times, over the active season in 2012 and 2013. A total of 32,237 specimens were identified, representing 200 species and 6 families, including two new continental records, Hylaeus communis Nylander (1852) and Anthidium florentinum (Fabricius, 1775). Despite high community evenness, we found significant abundance of diverse species, including exotic ones. Spatio-temporal analysis showed higher stability in the most urbanized city (Montreal) but low nestedness of species assemblages among the three urban habitats in both cities. Our study demonstrates that cities are home to diverse communities of wild bees, but in turn affect bee community structure and dynamics. We also found that community gardens harbour high levels of functional trait diversity. Urban agriculture therefore contributes substantially to the provision of functionally diverse bee communities and possibly to urban pollination services.

A. Boilard, and A. Duclos for their help in the lab and in the field. We thank M.-P. Lamy, C. Roy, G. Ayotte, and M. Paquet for their assistance in identifying flowers. We are also indebted to A. Beaudoin and É. Duchemin for logistic support, and to S. McIvor and J.-P. Lessard for their constructive comments on a previous version of the manuscript. Finally, special thanks to the managers of cemeteries and community gardens as well as the Management of Large Parks and Greening of the city of Montreal for allowing access to their sites. This study was funded by the National Science and Engineering Research Council of Canada (NSERC) Discovery Grant Program and the Fonds de Recherche Nature et Technologies Québec (FRQNT). The Bayesian analyses and goodness of fit tests were conducted on the Graham high performance computer clusters of Compute Canada.

We document a novel exotic bee for North America, Hylaeus (Hylaeus) communis Nylander, 1852 (Hymenoptera: Colletidae), and determine whether it is likely to spread widely across the continent. To evaluate the extent to which H. communis behaves as a generalist and would be able to adapt to novel North American environments, we compare the breadth of its climatic, floral, habitat, and nesting preferences between its native European range and sites where it was first discovered in southern Québec, Canada. Specifically, we calculate the paired difference index, which approximates species generalism, from a set of bipartite networks linking Hylaeus Fabricius, 1793 species to their respective floral hosts and habitats. Results indicate that H. communis is the most adaptable bee of the European Hylaeus fauna and will likely acclimate to its new environment, being a greater generalist than an already widely established exotic bee, H. hyalinatus Smith, 1842. In southern Québec, we find that, despite visiting a wide variety of flowering species, it exhibits a strong association with non-native plants and resides almost exclusively in urban settings. We hypothesise that H. communis will be able to spread widely throughout North America via multiple human-mediated but accidental dispersal events and by following the distribution of European weeds and horticultural plants.

The spatial heterogeneity of urban landscapes, relatively low agrochemical use, and species-rich floral communities often support a surprising diversity of wild pollinators in cities. However, the management of Western honey bees (Apis mellifera L.) in urban areas may represent a new threat to wild bee communities. Urban beekeeping is commonly perceived as an environmentally friendly practice or a way to combat pollinator declines, when high-density beekeeping operations may actually have a negative influence on native and wild bee populations through floral resource competition and pathogen transmission. On the Island of Montréal, Canada there has been a particularly large increase in beekeeping across the city. Over the years following a large bee diversity survey ending in 2013, there was an influx of almost three thousand honey bee colonies to the city. In this study, we examined the wild bee communities and floral resources across a gradient of honey bee abundances in urban greenspaces in 2020, and compared the bee communities at the same sites before and after the large influx of honey bees. Overall, we found a negative relationship between urban beekeeping, pollen availability, and wild bee species richness. We also found that honey bee abundance had the strongest negative effect on small (inter-tegular span <2.25 mm) wild bee species richness. Small bee species may be at higher risk in areas with abundant honey bee populations as their limited foraging range may reduce their access to floral resources in times of increased competition. Further research on the influence of urban beekeeping on native and wild pollinators, coupled with evidence-based beekeeping regulations, is essential to ensure cities contain sufficient resources to support wild bee diversity alongside managed honey bees.

With the growth of the insect farming industry, increasing quantities of insect manure (called frass) must be upcycled. This research provides one of the first sources of information regarding the potential plant growth enhancement of Tenebrio molitor's frass on garden plants. It aims at demonstrating that frass is a promising fertilizer for plant production. Nine vegetables, one herb, and three flowers were planted on the roof of "La Centrale Agricole" in Montreal. Plants were grown in a 5% compost-enriched substrate (v/v) (control) and fertilized with 0.5% (v/v) frass (treatment 2) or an isonitrogen concentration of hen manure (treatment 3). Plant growth (germination, height, N flowers) and productivity (biomass) were assessed regularly throughout the growing season. Although beets and carrots' seedling emergence was inhibited by both manures, this did not lead to reduced edible biomass compared to the control (germination was unaffected for corn, radish, and arugula). Similar to hen manure, frass resulted in a 16-fold increase of the edible biomass as compared to the control. Frass-fertilized plants had larger and more numerous flowers than control plants. Our results confirm that insect manure should be recognized as a suitable fertilizer for multiple crops, and should be regulated like other manures.