Aim Urbanization is associated with strong changes in biodiversity, but the diversity of plant and animal assemblages varies among urban habitats. We studied effects of urban habitats on the diversity of vascular plants and land snails in 32 large cities.Location Central Europe, Belgium and the Netherlands. MethodsThe species composition of all vascular plants that had not been planted by humans, and all land snails, was recorded in seven 1-ha plots within each city. Each plot contained one urban habitat type representing a different disturbance regime: historical city square, boulevard, residential area with compact building pattern, residential area with open building pattern, park, early successional and mid-successional site. For each plot, we obtained temperature and precipitation data. The effects of climate and habitat types on species composition were quantified using ordination methods with an adjusted variation partitioning algorithm. Differences in species composition among urban habitats were described using statistically determined diagnostic species, and differences in alpha, beta and gamma diversity were quantified.Results A total of 1196 plant and 87 snail species were recorded. Habitat type explained higher proportions of the total variation in both plant and snail species composition (11.2 and 8.2%, respectively) than did climate (4.6 and 6.3%). For both taxa, the main differences in species composition were observed between strongly urbanized sites in city centres and early successional and midsuccessional sites. For vascular plants, the number of species was lowest in city squares and boulevards, and highest at successional sites and in residential areas with compact building patterns. Beta diversity of vascular plants calculated for the same habitat types among cities was highest for squares and successional sites. The number of snail species was lowest in city squares and at early successional sites, and highest at mid-successional sites. The highest beta diversity of snail assemblages among cities was observed within the city square and early successional habitat types, and the lowest within residential area habitat types.Main conclusions Urban habitats differ notably in the diversity of their vascular plant flora and land snail fauna. Understanding the habitat-related biodiversity patterns in urbanized landscapes will allow projections of future impacts of urban land-use changes on the biota.

The species richness and composition of land snail assemblages in 42 floodplain forest sites along the Danube River in Slovakia were studied to find the main ecological gradients responsible for the variation in the faunas. We found just one, but steep, ecological gradient influencing the variation of snail species composition among different floodplain forest types, reflected in the first detrended correspondence analysis axis, which explained 29.6% of total variation. Site scores on this axis were significantly correlated with site humidity (r s ¼ 20.868; P , 0.001). Significant loading on the first axis was also found for flood frequency and several vegetation descriptors. Species composition mainly reflected differences between sites without floods and the others. Species richness as well as total abundances of live individuals were not significantly controlled by any explanatory variable, although some trends could be discerned. Considering vegetation classification, substantial differences were observed between wet softwood floodplain forests and the remaining types, drier softwood forests and different types of hardwood forests, which were impossible to distinguish based on land snail assemblages. The results are discussed in relation to earlier descriptive studies, and in terms of the conservation of these threatened habitats.