Ant brightness and size influence the seasonal vegetation use by ground-dwelling ants in an Amazonia-Cerrado transition zone

Several factors influence species distribution within communities, with ecological filters playing a major role by shaping morphological, physiological, and behavioral adaptations. Seasonal changes in environmental conditions—such as light incidence, temperature, and humidity—can favor species capable of foraging under varying conditions or in different strata. Ants are excellent models for studying how ecological filters structure communities throughout the year, as they exhibit traits that enable them to occupy a wide range of microhabitats. Two such traits that may reflect responses to environmental filters are body size and brightness. In this study, we investigated how ant distribution varies between soil and lower vegetation across two seasons, and how these patterns relate to ant morphology in an ecotonal area between the Amazon and Cerrado biomes. Ants were sampled using pitfall traps placed on the ground and in the lower vegetation. We measured the size and brightness of representative individuals from each species. A total of 2,659 occurrences were recorded, representing 237 species, 53 genera, and 8 subfamilies. Species richness was higher during the dry season, especially in the soil. Species turnover was the main component of beta diversity, although this pattern varied with season. During the rainy season, many ground-dwelling ants shifted to the vegetation, increasing the nestedness component in cross-strata comparisons. Larger ants were more frequent in vegetation, while smaller ants predominated in the soil. Darker individuals were more common in vegetation during the dry season; however, this seasonal migration of ground ants to the vegetation led to a lighter-colored ant community on average during the rainy season. These findings show that the ant community composition in the soil and lower vegetation is not stable year-round. Seasonal climatic conditions influence foraging activity and species presence, highlighting the importance of seasonal dynamics and vertical stratification in shaping community structure.