Association of giant ant Dinoponera quadriceps nests with termite mounds and landscape variables in a Caatinga dry forest, Brazil

Abstract

Earth mounds, locally known as murundus, are ~ 4000 year old natural formations resulting from termite excavation and occur as mound fields in the Caatinga, the largest dry forest region in South America. Termites are ecosystem engineers and the bioturbation caused by them can influence the colonization of other insect species, e.g., the giant ants Dinoponera quadriceps, which are conspicuous in mound fields. We hypothesized that (i) nests and individuals of giant ants are more prevalent in mound fields when compared to regions in Caatinga with no earth mounds, (ii) nests may be located close to trees with large trunks, and (iii) amidst soils rich in organic matter. We placed sampling plots in four sites: two mound fields and two sites with no earth mounds in the state of Bahia, Brazil. Ant nests were more abundant in mound fields when compared to areas with no earth mounds. Thus, mound fields are important sites for ant nests at the landscape scale. The nests were more often found between mounds where termite tunnels occur, suggesting that ants avoid nesting on the top of earth mounds which are bare resulting from anthropogenic removal of vegetation and litter over the past few decades. Thus, the continued conversion of Caatinga into pasture may endanger populations of D. quadriceps, similar to the fate of D. lucida in the Atlantic Forest. The local extinction of the giant ant that are important seed dispersers in this biome can result in the impoverishment of Caatinga floristic structure and diversity.