Distribution of the Fire Ant (Hymenoptera: Formicidae) Hybrid in Georgia

Abstract

The red imported fire ant, Solenopsis invicta Buren, and the black imported fire ant, S. richteri Forel, are reproductively isolated in their native South America even where their ranges overlap (Ross and Shoemaker 2005, Mol. Ecol. 14: 3,419-38). Yet, these invasive ant species readily hybridize in their expanded ranges in North America. Vander Meer and Lofgren (1988, Florida Entomol. 71: 232-32) determined that hybridization occurred in south Alabama soon after the invasion of these ant species. Hybrid ants are morphologically similar to S. richteri and S. invicta, and chemical analysis of ant venom and cuticular hydrocarbons or genetic characterization are required to distinguish hybrid ants from the parent species (Vander Meer et al. 1985, Florida Entomol. 68: 501-06; Ross et al. 1987, Evol. 41: 280-93). Drees et al. (2006, Texas Coop. Ext. B-6043) recently showed S. richteri distributed in only 8 counties in northern Mississippi and 10 counties in west central Tennessee. The S. richteri x S. invicta hybrid, however, is more widely distributed in southern Tennessee, the western tip of North Carolina, and northern areas of Mississippi, Alabama, and Georgia. Although hybridization occurred upon arrival of these two species in North America, S. invicta now occupies the remaining quarantined areas in North America (see http://aphis.usda.gOV) owing to its apparent displacement of S. richteri and the hybrid in this expanded range. Diffie et al. (1988, J. Entomol. Sd. 23: 187-91) initially reported the discovery of the hybrid ant in Alabama and Georgia and mapped its known distribution in Georgia, Alabama and Mississippi. Their survey included ants collected from 20 counties in Alabama and 11 counties in Georgia. The survey reported herein expands those