Changes of isopod assemblages along an urban-suburban-rural gradient in Hungary

Responses of isopod assemblages to urbanisation were studied along an urban-suburban-rural gradient representing a decrease in the intensity of human disturbance. Pitfall trapping collected six species (Armadillidium vulgare, Porcellio scaber, Porcellium collicola, Trachelipus ratzeburgii, Cylisticus convexus, and Trachelipus rathkii). A. vulgare occurred abundantly in all sites reflecting the broad tolerance and invasive nature of this species. Indicator species analysis demonstrated that P. scaber and T. rathkii were significant quantitative character species for the urban site, while T. ratzeburgii was characteristic for the natural habitats (suburban and rural sites). CANOCO revealed that ground and air temperature show positive correlation with the distribution of P. scaber and T. rathkii, and negative correlation with T. ratzeburgii. Nested ANOVA on trap level showed that there were no significant differences between the number of isopod species and individuals, and the diversity of isopod assemblages in the three studied areas. Significant differences were observed at site level. The results did not support the hypothesis that 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. Multivariate methods detected that the isopod assemblages of the rural and suburban areas were relatively similar, while that of the urban area was relatively separated.