A species-level comparison of occurrence patterns in carabids along an urbanisation gradient

Abstract

The activity–density pattern of frequent carabid species was studied using pitfall traps in forest patches along an urbanisation gradient defined in terms of the ratio of the built-up area to the natural habitat. We predicted that the activity–density of the forest specialist carabid species should decrease from rural sites to the more altered urban ones. We also predicted, that there is no unique pattern for the generalist species, because the activity–density pattern is controlled by their autecological characteristics in a complex interaction with the environmental variables, and urbanisation/disturbance level. Moreover, we identified the environmental factors responsible for the observed variation in carabid activity–density. As predicted, the activity–density of two forest specialist species ( Carabus convexus, Pterostichus oblongopunctatus) decreased significantly from rural sites to urban ones. The activity–density of the generalist species, Amara convexior, was higher in the heavily disturbed urban sites. The generalist species, Ophonus nitidulus, was significantly more abundant in the rural sites. The other five frequent generalist species ( Notiophilus rufipes, Pterostichus melanarius, Harpalus luteicornis, Pterostichus niger, Stomis pumicatus) showed no significant changes in activity–density along the gradient. The two open-habitat species ( Anisodactylus nemorivagus, Bembidion lampros) also showed no significant changes in activity–density along the gradient. Canonical correspondence analysis highlighted that the variation in the activity–density of the studied species was related to the following environmental factors: ground temperature, air temperature, relative humidity, leaf-litter cover, cover of decaying wood material, herbs, shrubs, and to the amount of prey items.