Multiscale Effects of Urbanization on Ant Diversity and Functional Composition in Urban Green Spaces

Urbanization exerts complex impacts on biodiversity, operating across multiple spatial scales and through interactions between landscape variables and local environmental conditions. In this study, we evaluated how different dimensions of urbanization affect taxonomic and functional diversity, as well as the composition in an ant community living in urban green spaces in Salvador, Bahia, Brazil. Ants were sampled at 62 sites distributed across four types of urban green areas (medians, forest fragments, public squares, and vacant lots) using Winkler traps on the ground and bait lines in the arboreal vegetation. After identification, each species was classified into functional groups. We measured environmental variables (including litter depth, herbaceous cover, among others) and landscape metrics (population density, percentages of impervious surface, forest cover, total green area, as well as patch and edge densities) at spatial scales ranging from 50 m to 1,000 m. A total of 93 ant species were collected, representing 40 genera and six subfamilies. For species richness, two models showed the best fit: one incorporating population density at 1,000 m, and another including the proportion of green areas at 50 m. In the first model, population density and litter depth were positive predictors. In the second, only litter depth and the proportion of green area within forest fragments had positive effects. Functional group richness was best explained by the density of herbaceous patches; however, only litter depth had a significant effect. We observed that the functional composition of ants is shaped by large-scale landscape variables (1,000 m) and local factors. Litter depth favored hypogeic ants and fungus growers, while limiting arboreal species; forest cover benefited arboreal ants and fungus growers; urbanization favored omnivores, whereas forest edges were associated with predators. Conserving the diversity and ecological functions of ant communities in urban environments requires integrating strategies that act simultaneously at multiple scales, preserving both the variety of green spaces and local microenvironmental conditions.