Abstract: We compared the ant assemblages from four very heterogeneous habitats over a short-distance elevational gradient of vegetation (due to the presence of an inselberg) at the Nouragues Research Station, French Guiana. We focused on litterdwelling ants, combining the use of pitfall traps and the Winkler method according to the Ants of the Leaf Litter Protocol. This permitted us to note (1) a high leaf-litter ant diversity overall and a decreasing diversity gradient from the lowland rainforest to the top of the inselberg, and (2) differences in species density, composition and functional structure. While the ant assemblages on the plateau and inselberg can be considered functionally similar and typical of an Amazonian rainforest, that of the transition forest, relatively homogenous, rather corresponded to an ant fauna typical of open areas. By contrast, the liana forest assemblage was unexpectedly richer and denser than the others, sheltering a litter-dwelling ant fauna dominated by numerous and abundant cryptic species. These taxonomical and functional dissimilarities may reflect the influence of the environmental heterogeneity, which, through variable abiotic conditions, can contribute to maintaining a notably rich ant biodiversity in these Neotropical habitats.