Impact of exotic pastures on epigeic arthropod diversity and contribution of native and exotic plant sources to their diet in the central Brazilian savanna

Abstract

Much of the Brazilian savanna (known locally as the Cerrado) has been converted to pasture of African C4 grasses (exotic pastures) for livestock production. The resulting habitat simplification and decreased resource availability may be significant factors underlying the impact on some soil arthropod groups, although it is still unclear how the different soil groups respond to this impact in the Brazilian savanna. We sampled epigeic arthropods in exotic pastures, adjacent woodland savanna fragments (cerrado sensu stricto), and savanna-pasture boundaries to investigate the impact of pasture on their diversity and activity, identifying the arthropods that contribute most to the between-habitat dissimilarities and those most vulnerable to pasture implementation. We also estimated the contribution of native and exotic plants to the diets of frequently observed arthropods in each habitat using carbon and nitrogen stable isotope analysis. We found lower richness and diversity of epigeic arthropods in pastures, where we also observed decreased activity of predator groups, whereas the activity of Symphypleona and Poduromorpha springtails increased. Springtail orders and Myrmicinae morphospecies were the main contributors to the between-habitat dissimilarities. Staphylinidae, Ptiliidae, and Zodariidae morphospecies seem to be vulnerable to exotic pastures. Our isotopic models show that woodland savanna arthropods feed preferentially on native C3-plant sources, while also showing signs of exotic C4 sources in their diet. These outcomes indicate that foraging or dispersal events may occur between habitats since arthropods captured in pastures also show signs of native sources in their diet.