Fire and flood: How the Pantanal ant communities respond to multiple disturbances?

Abstract

Disturbances are key events in ecological systems, strongly impacting biological communities. This study disentangles the effects of a chronic (flood) and acute (fire) disturbance to determine their interactive effects on ant species richness and composition at different temporal scales. For this, we sampled ground-dwelling ants with pitfall traps on native grasslands in the Pantanal wetland, one of the world's largest floodplains. We sampled ants ten days (short-term), one year (medium-term), and four years (long-term) after fire and at varying elevations (a surrogate for the time that these areas remain flooded). We found that fire was the dominant factor in determining ant community patterns in flooded areas. In the short-term, fire substantially changed species composition and increased species richness. However, these effects decreased at one year and disappeared after four years, demonstrating the ant community’s resilience. Elevation and, consequently, flooding, did not influence any measured parameter, indicating that the ant species are adapted to colonize other areas rapidly or survive in such flooded habitats. Our results suggest that Pantanal ant communities can recover from acute fire disturbances after some years. However, increasing fire frequency caused by global climatic changes and recent Brazilian environmental policy misconducts would probably compromise the observed resilience.