Fine-scale heterogeneity across Manhattan's urban habitat mosaic is associated with variation in ant composition and richness

1. Global urbanis ation is rapidly expanding and most of the world’s humans now live in cities. Most ecologi cal studies have, however, focused on protected areas. 2. To address this issue, we tested predictions from studies of protected areas in urban ecosystems. 3. Because most cities are heterogeneo us habitat mosaics which include habi- tats with varying levels of chronic environmental stress, we focused on predic- tions from studies of less modi?ed ecosystems about community-wi de responses to variation in chronic stress. 4. We sampl ed ants across Manhattan’s urban habitat mosaic, at sites with varying levels of chronic environmental stress. 5. Many predictions derived from less modi?ed ecosystems were supported by our ?ndings: despite being the most intensively sampled habitat, high stress urban medians ha d less variability in ant composition –both within and among sites – than either urban parks or urban forests, the lowest stress habitat – urban forests-had signi?cantly more accumulated species and a higher number of unique species than higher stress habitats, and urban parks, which have intermediate levels of chronic environmental stress, also had intermediate levels of variation in among-site species composition, accumulated species richness, and the incidence of unique species. The most common species also differed across Manhattan’s urban habitat mosaic. 6. Nevertheless, the prediction that exotic species would occur more fre- quently in higher stress habitats was not supported; exotic species were equally common across all habitats. 7. These ?ndings suggest that ?ne -scale heterogeneity in the chronic stress of urban habitats may be an underappreciated, but important structuring force for urban animal communities.