Biogeographic effects of red fire ant invasion

The red imported fire ant, Solenopsis invicta, was accidentally introduced to North America over 60 years ago and has spread throughout the southeaste rn United States. We document the biogeographic consequences of this invasi on. We censused ground-foraging ant communities on a 2000 km transect from Florida through New York that passed through invaded and intact biotas. Nat ive ant species density peaks at mid-latitudes in the eastern United States , and the location of this peak corresponds to the range limit of S. invict a. In uninvaded sites, ant species co-occur less often than expected by cha nce. In the presence of S. invicta, community structure converges to a rand om pattern. Our results suggest that the effects of S. invicta on native an t communities are pervasive: not only does the presence of S. invicta reduc e species density at local scales, it alters the co-occurrence patterns of surviving species at a biogeographic scale.