INVASION OF POLYGYNE FIRE ANTS DECIMATES NATIVE ANTS AND DISRUPTS ARTHROPOD COMMUNITY

The fire ant Solenopsis invicta invaded SE USA from South America >50 yr ago. Increasing frequencies of polygyne or multiple-queen fire ants are disturbing because nest densities of this new form are often 10 times as great as those of the monogyne form. In C Texas, invasion decimated the indigenous ant fauna largely through competitive replacement. Species richness of ants in infested areas dropped by 70%, while the total number of native individuals dropped by 90%. Of 35 species of ants collected, 23 were either significantly less common or absent from infested sites; only S. invicta was more common at infested sites. The most dramatic effect of the invasion was a 10-30 fold increase in the total number of ants at infested sites - of which >99% were S. invicta. Abundance of isopods, erythraeid mites, and tumblebug scarabs declined significantly, while the abundance of ground crickets, a brachypterous roach, and a symbiotic scarab increased significantly. Overall, the species richness of non-ant arthropods was 330% lower in infested sites, and individual numbers were 75% lower. Total arthropod species richness (including ants) was 40% less at infested sites. -from Authors