Many bee species are declining globally, but to detect trends and monitor bee assemblages, robust sampling methods are required. Numerous sampling methods are used, but a critical review of their relative effectiveness is lacking. Moreover, evidence suggests the relative effectiveness of sampling methods depends on habitat, yet efficacy in urban areas has yet to be evaluated. This study compared the bee community documented using observational records, targeted netting, mobile gardens, pan traps (blue and yellow), vane traps (blue and yellow), and trap‐nests. The comparative surveys of native bees and honeybees were undertaken in an urbanized region of the southwest Australian biodiversity hot spot. The outcomes of the study were then compared to a synthesis based on a comprehensive literature review of studies where two or more bee sampling methods were conducted. Observational records far exceeded all other methods in terms of abundance of bees recorded, but were unable to distinguish finer taxonomic levels. Of methods that captured individuals, thereby permitting taxonomic identification, targeted sweep netting vastly outperformed the passive sampling methods, yielding a total of 1324 individuals, representing 131 taxonomic units—even when deployed over a shorter duration. The relative effectiveness of each method differed according to taxon. From the analysis of the literature, there was high variability in relative effectiveness of methods, but targeted sweep netting and blue vane traps tended to be most effective, in accordance with results from this study. However, results from the present study differed from most previous studies in the extremely low catch rates in pan traps. Species using trap‐nests represented only a subset of all potential cavity‐nesters, and their relative abundances in the trap‐nests differed from those in the field. Mobile gardens were relatively ineffective at attracting bees. For urbanized habitat within this biodiversity hot spot, targeted sweep netting is indispensable for obtaining a comprehensive indication of native bee assemblages; passive sampling methods alone recorded only a small fraction of the native bee community. Overall, a combination of methods should be used for sampling bee communities, as each has their own biases, and certain taxa were well represented in some methods, but poorly represented in others.

Loss of natural habitat through land‐use change threatens bees. Urbanisation is a major, increasing form, of habitat loss, and a novel, pervasive form of disturbance known to impact bee diversity and abundance in a variety of often inconsistent ways. We conducted a comprehensive, semi‐quantitative review, involving 215 studies, on responses of bees to urban landscapes, and local and landscape variables proposed to influence bee abundance and diversity. Urban areas tend to be favourable habitat for bees compared with agricultural ones, but compared with natural areas, urban areas often host more abundant populations yet fewer species. Factors associated with urban landscapes, including changes in foraging resources and nesting substrate types and availability, contribute to changes in abundance, species richness, and composition of native bee assemblages. However, the conclusions of studies vary greatly because of the difference in the ecological traits of bees, habitats surveyed, and geographic region, as well as noise in the data resulting from inconsistencies in sampling methodology, and definitions of ‘urban’ and ‘natural’. Identifying what biotic and abiotic features of cityscapes promote or threaten the persistence of urban bee diversity is critical. We provide a comprehensive evaluation of how bees (both in aggregate and according to their ecological guild) have responded to the urban environment, identify gaps in knowledge in urban bee ecology, and make recommendations to advance our understanding of bees in urban environments to promote conservation of diverse bee communities.

Animal pollinators are vital for the reproduction of ~90% of flowering plants. However, many of these pollinating species are experiencing declines globally, making effective pollinator monitoring methods more important than ever before. Pollinators can leave DNA on the flowers they visit, and metabarcoding of these environmental DNA (eDNA) traces provides an opportunity to detect the presence of flower visitors. Our study, collecting flowers from seven plant species with diverse floral morphologies, for eDNA metabarcoding analysis, illustrated the value of this novel survey tool. eDNA metabarcoding using three assays, including one developed in this study to target common bush birds, recorded more animal species visiting flowers than visual surveys conducted concurrently, including birds, bees, and other species. We also recorded the presence of a flower visit from a western pygmy possum; to our knowledge this is the first eDNA metabarcoding study to simultaneously identify the interaction of insect, mammal, and bird species with flowers. The highest diversity of taxa was detected on large inflorescence flower types found on Banksia arborea and Grevillea georgeana. The study demonstrates that the ease of sample collection and the robustness of the metabarcoding methodology has profound implications for future management of biodiversity, allowing us to monitor both plants and their attendant cohort of potential pollinators. This opens avenues for rapid and efficient comparison of biodiversity and ecosystem health between different sites and may provide insights into surrogate pollinators in the event of pollinator declines.

European honey bees have been introduced across the globe and may compete with native bees for floral resources. Compounding effects of urbanization and introduced species on native bees are, however, unclear. Here, we investigated how honey bee abundance and foraging patterns related to those of native bee abundance and diversity in residential gardens and native vegetation remnants for 2 years in urbanized areas of the Southwest Australian biodiversity hotspot and assessed how niche overlap influenced these relationships. Honey bees did not overtly suppress native bee abundance; however, complex relationships emerged when analysing these relationships according to body size, time of day and floral resource levels. Native bee richness was positively correlated with overall honeybee abundance in the first year, but negatively correlated in the second year, and varied with body size. Native bees that had higher resource overlap with honey bees were negatively associated with honey bee abundance, and resource overlap between honey bees and native bees was higher in residential gardens. Relationships with honey bees varied between native bee taxa, reflecting adaptations to different flora, plus specialization. Thus, competition with introduced bees varies by species and location, mediated by dietary breadth and overlap and by other life-history traits of individual bee species.