Changes in carabid beetle assemblages along an urbanisation gradient in the city of Debrecen, Hungary

Responses of carabid beetles (Coleoptera: Carabidae) to urbanisation were studied along an urban-suburban-rural gradient representing decreasing intensities of human disturbance. Carabids were collected by pitfall trapping during their activity period in lowland oak forest patches in the city of Debrecen, Eastern Hungary. The average number of carabid species was significantly higher in the rural and urban areas compared to the suburban one. The high overall species richness in the urban area was due to the presence of species preferring open habitats. The species richness of forest specialist carabids significantly increased along the urban-rural gradient. The overall carabid abundance was significantly higher in the rural than the other two areas. The results did not support the hypothesis that overall diversity should decrease in response to habitat disturbance. They also contradicted the intermediate disturbance hypothesis: species richness was not the highest in the moderately disturbed suburban area. In the urban area, opportunistic species dominated. The average carabid body size was significantly larger in the rural and suburban areas than in the more disturbed urban area. Multivariate methods detected changes in species composition and abundance structure along the urban-rural gradient. Significant proportion of the variation in abundance and species richness was explained by the heterogeneity of environmental variables (ground temperature, surface temperature, humidity, cover of decaying wood material, herbs, canopy layer, and by the amount of prey).