The ecology and behaviour of hover flies in urban ecosystems

Biodiversity is under threat from a range of transformative processes that humans have set in motion. It is critical that we understand how wildlife responds to these processes, to protect them from threats posed by them. Urbanisation is one of the most pervasive processes altering ecosystems and the way they function. Insect pollinators are pivotal to life on earth because they mediate the reproduction of most angiosperms, which–in turn–support the nutrient and energy cycles of most food webs. Concerns around declines in insect pollinators are common, yet the lack of understanding of the ecology of most insect species and how they respond to urbanisation is a major gap in our knowledge. I used a combination of multi-scale survey techniques and analytical methods to explore the factors that affect the diversity, abundance, and behaviour of hover flies in urban ecosystems. Hover flies are an important group of floral visitors and pollinators commonly found in urban areas. I found that hover flies respond to their environments at multiple spatial and temporal scales. At the intraspecific scale, male and female hover flies have differences in behaviour; at the interspecific scale, hover flies and honeybees use floral resources in different ways; at the local scale, hover fly diversity and abundance depend on the richness and abundance of flowers; at the urban landscape scale, hover fly diversity and abundance are affected by human population density; and at the regional scale, hover fly species respond to seasonal variation being most abundant and diverse in winter. The outcomes of my research highlight the importance of multi-season studies. Additionally, observations on the ecology of hover flies are made, which may be used by researchers to explore aspects of pollination and pest control by hover flies. Finally, I provide evidence-based recommendations to improve biodiversity outcomes in urban greenspaces.