Conservation of biodiversity in landscape mosaics requires us to understand the impacts of human land use within mosaic elements and an evaluation of the biological uniqueness of different elements. We examined patterns of ant diversity in three semiarid rangeland landscapes used predominantly for grazing. Within each landscape, we compared the effects of grazing and natural variation in soils and vegetation on ant diversity and community composition. Grazing had little effect on ant richness, diversity, or composition at the transitional zone or the desert grassland site; but, ungrazed areas at the shortgrass steppe site had a higher overall richness and favored the abundance of some species. Some samples of saltbush (Atriplex canescens) shrubland were similar to ungrazed samples in richness and species composition. In both the transitional zone and the desert grassland, creosotebush (Larrea tridentata)-dominated habitats harbored comparatively species-rich and distinct ant communities. Also, mesquite (Prosopis glandulosa) coppice dunes at the desert grassland site favored the abundance of several rare species. Canonical correspondence analysis revealed that variation in soil hardness and texture best explained community variation at the shortgrass steppe site, whereas soil texture and associated differences in shrub density best explained differences in composition at the transitional and desert grassland sites. While habitat characterization based on vegetation classification did not adequately reflect environmental variation important to ants in shortgrass steppe, it reflected important soil textural variation in the transitional and desert grassland sites. This suggests that ant conservation in these semiarid rangelands should emphasize patterns of variation in soil properties.