Responses of carabid beetles to urbanization in Transylvania (Romania)

To investigate the impact of urbanization on carabid beetles samples were taken over two years using pitfall traps along a rural-urban forest gradient representing increasing human disturbance in and nearby the city of Sfantu Gheorghe (Romania). We predicted that total number of species should decrease, whereas number of opportunistic and matrix species should increase towards the urban end of the gradient. Both the overall species richness and the number of individuals were significantly the highest in the suburban area followed by the rural area and the lowest in the urban area. These findings contradicted the increasing disturbance hypothesis; the number of species did not decrease by the increasing disturbance. The proportion of the forest specialist individuals and species significantly decreased from the rural towards the urban area, supporting the habitat specialist hypothesis. An opposite pattern was observed in species richness of the generalist carabids, supporting the opportunistic species hypothesis. Both the proportion of matrix species and their density were significantly higher in the urban area, supporting the matrix species hypothesis. Our findings also highlighted that overall diversity is not an appropriate indicator; species with different habitat affinities should be analysed separately to evaluate the real effect of urbanization. (C) 2011 Elsevier B.V. All rights reserved.