The importance of fragmentation and habitat quality of urban grasslands for butterfly diversity

Parks, remnants of natural habitats and other green areas are important for preserving biodiversity in urban areas. Here, we investigate the relative importance of habitat type and connectivity for butterfly species richness in the city of Malmo, Sweden. Further, we compare species richness and composition in the urban habitats with that in the surrounding agricultural landscape using previously published data. Both butterfly species richness and density increased with decreasing connectivity, measured as the proportion of urban green areas within I km, and were higher in ruderal sites than in traditional and semi-natural parks. Species richness was only slightly lower in the urban habitats than in semi-natural grassland remnants in the agricultural landscape surrounding the city and there was only a small difference in (between site) diversity between urban and semi-natural landscapes. This study highlights the importance of "townscape" composition for species richness in urban habitats but also, demonstrates clearly that urban habitats, especially those characterized by an early-successional stage, can be of relatively high conservation value in regions dominated by intensive human land use. (C) 2009 Elsevier B.V. All rights reserved.