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United States Department of Agriculture

Agricultural Research Service

Title: Distribution of the fire ant (Hymenoptera: Formicidae) hybrid in Georgia)

item Gardner, Wayne
item Diffie, Stan
item Vander Meer, Robert - Bob
item Brinkman, Mark

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2007
Publication Date: 1/1/2008
Citation: Gardner, W.A., Diffie, S., Vander Meer, R.K., Brinkman, M.A. 2008. Distribution of the fire ant (Hymenoptera: Formicidae) hybrid in Georgia. Journal of Entomological Science. 43:133-137.

Interpretive Summary: The high population densities of the red imported fire ant, Solenopsis invicta the black imported fire ant, S. richteri, and their viable hybrid in the southern and southeastern United States cause serious medical, agricultural, electrical, and ecological problems. Knowledge about their current distribution is important in understanding their future spread. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida, and the Department of Entomology at the University of Georgia, Griffin, Georgia systematically surveyed the counties in Northern Georgia for fire ants and found that counties that previously did not have fire ants were now infested with hybrid fire ants, even the more mountainous areas of northwestern Georgia. This also confirms that hybrid fire ants are more adaptable to cooler environments and may be able to out compete both of its parental lines. These data will help predict the further spread of the fire ant in the United States and elsewhere.

Technical Abstract: Invasive black and red imported fire ants were found to hybridize in the United States over 20 years ago, and the hybrids were reproductively viable. Morphologically the hybrid is difficult to distinguish from its black parent, however, venom alkaloid and cuticular hydrocarbon patterns are very distinctive taxonomic tools. Using this method the hybrid form was found to occupy large areas of northern MS, AL, and parts of northwestern GA. This work further delineates the southern and eastern boundary of the hybrid zone in Georgia. In 1985, 23 counties across northern Georgia were not infested with imported fire ants. Only 11 counties were not infested in 1995, and the present work shows all counties were infested by 2000. The invasion of these northern, more mountainous counties was apparently by hybrid ant populations, as evidenced in the survey results reported herein. This is further supported by the postulation that S. richteri, whose native range is temperate areas of Argentina, and the S. richteri x S. invicta hybrid are better adapted to cooler more northern latitudes than S. invicta in their expanded North American ranges. These data will help predict the further spread of the fire ant in the United States and elsewhere.

Last Modified: 05/26/2017
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