Seasonal variation in floral resource use by a hover fly (<i>Melangyna)</i> (Diptera: Syrphidae) and the western honey bee (<i>Apis mellifera)</i> (Hymenoptera: Apidae) in an urban setting

Concerns about the impacts of introduced honey bees (Apis mellifera L.) on native insects and pollination services are prevalent. These impacts may be more pronounced on urban greenspaces, yet research on the use of abundant winter-flowering plants, such as Acacia spp. and Grevillea spp., in subtropical ecosystems is limited. Our study investigated the seasonal use of floral resources by honey bees and native hover flies (Melangyna indet.) in urban greenspaces of varying urbanization levels in Sydney, Australia. We found both insect groups use similar plants, with honey bees having a higher number of interactions with plants in general, but Melangyna interacting with more plant species during some seasons. Particularly in autumn and winter, when native plants flower, Melangyna had more interactions and visited more plant species than honey bees. The overlap in floral resources used by both was higher than expected in various urbanization levels during spring and autumn. This suggests that Melangyna may play a significant role in pollination during autumn and winter, especially in highly urbanized sites. The observed differences in floral resource utilization and seasonal variations indicate that the potential effects of introduced A. mellifera on native pollinators like Melangyna may be difficult to quantify given the high number of variables and complexity of the system. Our findings underscore the importance of considering seasonal patterns and multispecies interactions in studies on the impact of introduced species on native biodiversity.