Urbanization structures urban insect communities in aquatic microhabitats

Abstract More and more people are living in cities and cities are predicted to increase in size and number. Urbanization may have several effects on biodiversity. However, these effects can be species (or taxon) specific and may be dependent on the measured urbanization variables. Water-filled tree holes constitute breeding habitats for a range of insects and may be used as model systems to investigate effects of anthropogenic change such as urbanization. Even in cities these and other small standing waters are colonized by aquatic insects. Using a Citizen Science Project, we investigated how urbanization (imperviousness, altered temperature, building density, etc.), environmental parameters (pH, O2) and detritus serving as a food source affect aquatic larval insect communities and leaf-litter decomposition in artificial aquatic microhabitats resembling tree holes in the city of Salzburg, Austria. We found that these artificial containers were colonized by a broad range of insect species. Detritus content partly explained larval abundance. Urbanization however, measured as imperviousness and human population density, predicted shifts in community composition, especially contrasting patterns between the mosquito species Culex pipiens and Aedes japonicus. Urban microhabitats could be shown to be important habitats for aquatic insects. However, with increasing urbanization, aquatic communities mainly consist of midges, for example mosquitoes and ceratopogonids, potentially threatening human health via pathogen transmission. Therefore, we suggest improving citizen information on possible measures preventing the establishment and spread of harmful species while still supporting native biodiversity in urban spaces.