Carabid beetle assemblages (Coleoptera, Carabidae) across urban-rural gradients : an international comparison

We studied communities of carabid beetles in residual forest patches along urban-suburban-rural gradients in three cities (Helsinki, Finland; Sofia, Bulgaria and Edmonton, Canada) to examine their responses to urbanisation. Only Finnish carabids showed a marked division of community structure along the gradient. In Bulgaria and Canada, carabids did not separate into distinct urban, suburban and rural communities. Our results provide some support for the predictions that species richness will decrease, that opportunistic species will gain dominance, and that small-sized species will become more numerous under disturbance such as that provided by urbanisation. The rather weak and varied response of carabids to this disturbance suggests that local factors and their interaction are of primary importance for community composition. Occurrence of reasonably similar carabid communities across the gradient at each of the three levels of urbanisation suggests that habitat changes commonly associated with urbanisation have not affected the ecological integrity of carabid assemblages in residual urban forest patches