The impacts of urbanisation on the ecology and evolution of dragonflies and damselflies (Insecta: Odonata)

Urbanisation is one of the main drivers of ecosystem change. The impacts of urban land use on biodiversity have been investigated, but other aspects of ecology have been overlooked, as well as the effects of urban stressors. Understanding the effects of specific urban stressors is crucial in order to appropriately manage urban areas and conserve their biodiversity. Dragonflies and damselflies (the Odonata) are a suitable taxon for evaluating the impacts of urbanisation on both terrestrial and aquatic ecosystems. Here, using a combination of field and laboratory data, I study the ecological impacts of urban stressors on odonates. I found that the urban heat island has negligible impacts on the phenology of odonates compared to climate change. Moreover, noise disturbance reduces significantly the feeding rate of the damselfly Ischnura elegans, although anthropogenic noise has no significant impact. Regarding the impacts of polarised light pollution (PLP), the strength of polarotaxis increased significantly with age in laboratory-reared specimens, but there was no significant differentiation between urban and rural populations. However, field-caught urban specimens showed less preference to polarised light compared to rural populations, suggesting strong selective pressures are acting upon urban populations, but no adaptation has occurred. Flight-related traits showed no significant differentiation among urban and rural populations of I. elegans. Lastly, biodiversity patterns did not differ among urban and rural areas, although aquatic vegetation and presence of fish were the main drivers of community composition. These results show odonates can tolerate a wide range of urban stressors, notably I. elegans. However, PLP, fish, and absence of aquatic vegetation in urban ponds can have a negative impact on odonate biodiversity, which has important implications on conservation and management of urban areas. Urban ecosystems are complex, thus an integrative approach is necessary in order to understand in depth the impacts of urbanisation on biodiversity.