In South America, Solenopsis saevissima and S. invicta are the most common fire ants. Nests are founded in areas under anthropic interference like urban or rural areas, but S. invicta is found preferentially in those with the greatest anthropic interference. However, we do not know the rates at which they exist in anthropized areas next to high density of native vegetation. Areas with 60 to 90% of native Atlantic Forest were selected to verify the occurrence of both species in rural and urban areas. We investigated the molecular diversity and applied the reconstruction of the ancestral state analysis for each species. A total of 186 nests were analyzed and we found that the two species had the same proportion in the urban area. However, S. saevissima had a higher rate of prevalence in the rural area, in addition to having a greater number of haplotypes and ancestry associated with this type of habitat for the region. S. invicta had the same number of haplotypes in both rural and urban regions, and less haplotypic diversity. We conclude that S. saevissima is a species typically associated with rural areas and S. invicta, although present, is not dominant in urban areas.

Urban parks offer refuge for numerous animal species, and some of these parks represent the remaining fragments of native forests. We evaluate the diversity and composition of epigaeic ant species (Hymenoptera: Formicidae) in urban parks located within the Atlantic Forest biome (Centenial Park, Leon Feffer Park and Villa Lobos Park). For our collections, we placed pitfall traps along 100-m line transects in areas both accessible and inaccessible to the public. A total of 46 species distributed in seven subfamilies were collected. The number of species did not differ among park areas, but the ant communities themselves differed. Native species, such as Strumigenys denticulata and S. louisianae, were collected in the most preserved natural areas in the parks. Generalist species composed the richest guild and were primarily found in areas with public access. Wasmannia auropunctata, Brachymyrmex heeri, Solenopsis sp. 2, and Solenopsis sp. 3 were classified with high value as biological indicators.