Invasion of Camponotus punctulatus ants in sown pastures: consequences for ant activity and diversity

Abstract

Agricultural activity in NE Argentina promotes the demographic explosion of the ant Camponotus punctulatus Mayr. We compared ant activity between a natural grassland and a neighbouring sown pasture in north-eastern Argentina during 24 h periods during three different times in the year. We offered sugar and tuna baits to ants in order to assess ant foraging activity. We set pitfalls during the summer to quantify ant activity independently of their responses to food resources. We also used bait and pitfall data to estimate ant diversity. C. punctulatus was the single ant species present at baits in the sown pasture. Significantly greater numbers of C. punctulatus in comparison to other ants were found at pitfalls at the agriculturally-disturbed plot when compared with the natural grassland, although no differences in ant species richness were observed between plots. C. punctulatus was active throughout the day. Foraging of the ant community differed significantly between the sown pasture and the natural grassland. Foraging activity of C. punctulatus and all other ant species exhibited opposite patterns in the natural grassland. The successful establishment of C. punctulatus after agricultural disturbance seemed to have a negative effect on the foraging patterns of the ant community through a change in the relative abundance of ant species.