Résumé:
Urbanized areas are rapidly expanding into a variety of habitats. Urbanization and suburbanization are often associated with changes in biodiversity, which are natu- rally influenced by biotic interactions and abiotic habitat characteristics. The main cause of changes caused by suburbanization is fragmentation. Its impacts vary between animals with different dispersal abilities. We focused on studying the responses of three taxa with different dispersal abilities: birds as a relatively high-dispersal taxon, medium-dispersal butterflies, and low-dispersal land snails. We studied how biotic factors as well as habitat structural and fragmentation char- acteristics explain the community composition of the three study taxa in urban grasslands in the city of Pardubice (Czech Republic). Birds were the most species-rich taxon followed by butterflies. Land snails had species-poor grassland communities. Species composition analysis indicated species overlap among the studied taxa. Bird species composition covaried with butterfly species richness and reciprocally. Both taxa were significantly influenced by the amount of woody vege- tation within the grassland. Bird community composition was also influenced by fragmentation characteristics, namely the distance to the nearest built-up area. Urban growth most likely leads to changes in the characteristics of animal commu- nities associated with former lowland natural grasslands, deteriorating the commu- nities of low-dispersal land snails while allowing birds that have generally higher dispersal abilities to thrive. Our results show that in assessing the impact of urbani- zation on biodiversity, attention should also be paid to low-dispersal animal taxa.
