LONG-TERM IMPACTS OF AN ARTHROPOD-COMMUNITY INVASION BY THE IMPORTED FIRE ANT, SOLENOPSIS INVICTA

Invasive ant species represent a serious threat to the integrity of many ecological communities, often causing decreases in the abundance and species richness of both native ants and other arthropods. One of the most in-depth and well-known studies of this type documented a severe impact of the imported red fire ant, Solenopsis invicta, on the native ant and arthropod fauna of a biological field reserve in central Texas (USA) during the initial invasion in the late 1980s. I sampled the community again in 1999, 12 years later, utilizing the same methodology, to compare the short- and long-term impacts of this invasion. Pitfall traps and baits were used to obtain quantitative measures of the ant and arthropod community, and hand collecting was additionally employed to determine the overall ant species composition. Although the abundance and species richness of native ants and several other arthropod groups decreased precipitously immediately after the S. invicta invasion, all measures of native ant and arthropod species diversity had returned to preinvasion levels after 12 years. Solenopsis invicta was still the most abundant ant species, but not nearly as abundant as it was during the initial phase of the invasion. The results of this study indicate that the impact of such invasive ants may be greatest during and shortly after the initial phase of an invasion.