| The Red Imported Fire Ant, Solenopsis invicta, is native to South America. Since its accidental introduction, S. invicta has quickly spread throughout the southeastern US and farther, reducing or eliminating native ant species. Within the US, S. invicta is an economic pest, a public health concern, and a grave threat to native biodiversity. Little is known about the ecology of the fire ant in South America. The studies done have suggested that while S. invicta is a strong, aggressive competitor within its native range, it does coexist with many other species. Thus, most researchers believe that some factor is limiting S. invicta in South America, and have suggested competition from other ants, as well as native predators, pathogens, and parasites. Determining what limits S. invicta in its native range extends our understanding of community ecology and invasion biology, and may provide clues to controlling the ant in its introduced range.; I studied S. invicta in the Pantanal of Brazil. I found it to be strongly affected by competition from Camponotus rufipes and Paratrechina fulva. I believe S. invicta is able to coexist with these ant competitors because of a “dominance-discovery tradeoff.” I found that S. invicta loses agonistic encounters with C. rufipes and P. fulva, but is able to find resources faster than these other two ants. In the dry season, the high discovery ability of S. invicta allows it to harvest more than any other ant in the community. I also found evidence that S. invicta is more tolerant of dessicating conditions and thus is less restricted by abiotic factors than P. fulva.; The Pantanal exhibits a cycle of yearly flooding. I showed that although S. invicta prefers short grass habitat, it is forced to move into high grass to escape seasonal flooding. The high grass has higher concentrations of the two competitor species, and I suggest that S. invicta must pass part of every year on flood-refuge islands in intense competition with these superior competitors. This is the first work to suggest an effect of seasonal flooding on competition between fire ants and other ants. |
