The fire ant Solenopsis saevissima is a major pest frequent in human-disturbed areas of its native range where it forms 'supercolonies'. We determined that its natural habitat in French Guiana is likely the sporadically flooded riparian forest and aimed to evaluate this ant's impact on the abundance and diversity of other ants by comparing different habitats at two sites. We noted a significant decrease in ant species richness between the rainforest and human-disturbed habitats (but not between the former and the naturally disturbed riparian forest), and between extreme habitats and all others. The number of ant nests per surface unit (i.e., quadrats of equal surface area), a proxy of ant abundance, globally followed this pattern. S. saevissima was absent from pristine rainforest (as expected) and from extreme habitats, showing the limits of its adaptability, whereas some other native ants can develop in these habitats. Ant species richness was significantly lower in the presence of S. saevissima in the riparian forest, forest edges and meadows, illustrating that this ant species has a negative impact on the ant communities in addition to the impact of natural- and man-made disturbances. Only some ant species can develop in its presence, and certain of these can even thrive. Because it has been recorded in Africa, Guadeloupe and the Galápagos Islands, we concluded that, due to the increasing volume of global trade and forest destruction, S. saevissima could become a pantropical invasive species.