Does urbanization decrease diversity in ground beetle (Carabidae) assemblages?

Abstract

ABSTRACTAim We wanted to test whether urbanization has similar effects on biodiversity in different locations, comparing the responses of ground beetle (Coleoptera, Carabidae) assemblages with an urbanization gradient. We also wanted to see if urbanization had a homogenizing effect on ground beetle assemblages.Locations Nine forested temperate locations in Europe, Canada and Japan.Methods Published results of the Globenet Project were used. At all locations, three stages were identified: (1) a forested (rural) area, (2) a suburban area where the original forest was fragmented and isolated, and (3) remnants of the original forest in urban parks. These habitats formed an urbanization series. Study arrangements (number and operation of traps) and methods (pitfall trapping) were identical, conforming to the Globenet protocol. Assemblage composition and diversity patterns were evaluated. Diversity relationships were analysed by the Rényi diversity ordering method considering all ground beetles and – separately – the forest specialist species. Taxonomic homogenization was examined by multivariate methods using assemblage similarities.Results Overall biodiversity (compared by species richness and diversity ordering) showed inconsistent trends by either urbanization intensity or by geographic position. However, when only forest species were compared, diversity was higher in the original rural (forested) areas than in urban forest fragments. Within‐country similarities of carabid assemblages were always higher than within‐urbanization stage similarities.Main conclusions Urbanization does not appear to cause a decrease in ground beetle diversity per se. Forest species decline as urbanization intensifies but this trend is masked by an influx of non‐forest species. The rural faunas were more similar to the urban ones within the same location than similar urbanization stages were to each other, indicating that urbanization did not homogenize the taxonomic composition of ground beetle faunas across the studied locations.