Skip to main content
ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Imported Fire Ant and Household Insects Research » Research » Publications at this Location » Publication #194052
Title: GENETIC VARIATION AND STRUCTURE IN NATIVE POPULATIONS OF THE FIRE ANT SOLENOPSIS INVICTA: EVOLUTIONARY AND DEMOGRAPHIC IMPLICATIONS

Author
item ROSS, KENNETH - UNIVERSITY OF GEORGIA
item KRIEGER, MICHAEL - ROCKEFELLER UNIVERSITY
item KELLER, LAURENT - UNIVERSITY OF LAUSANNE
item Shoemaker, David

Submitted to: Biological Journal of the Linnean Society, London
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2007
Publication Date: 10/1/2007
Citation: Ross, K.G., Krieger, M., Keller, L., Shoemaker, D.D. 2007. Genetic variation and structure in native populations of the fire ant solenopsis invicta: evolutionary and demographic implications. Biological Journal of the Linnean Society, London.92:541-560.

Interpretive Summary: The red imported fire ant was inadvertently introduced from South America into the U.S.A. earlier last century. This ant species is considered a significant ecological, agricultural, and public health pest throughout its invasive range in the U.S.A. A scientist at the Center for Medical, Agricultural, and Veterinary Entomology, USDA, ARS, Gainesville, Florida describes here the results of a comprehensive population genetic study of fire ants from South America. A major finding of this study is that the different geographic populations of fire ants that were studied are strongly differentiated at both the nuclear and mitochondrial DNA genomes, with such differentiation significantly more pronounced in Brazil than Argentina. The presence of genetically unique regional populations in native fire ants, whether ultimately regarded as different biological species or not, has great practical relevance in that tracing the source of recently established invasive populations of fire ants around the globe should be feasible.

Technical Abstract: We studied population genetic variation and structure in the fire ant Solenopsis invicta using nuclear genotypic and mtDNA sequence data obtained from samples collected throughout much of its native range. The geographic populations that we studied are strongly differentiated at both genomes, with such structure significantly more pronounced in Brazil than Argentina. Higher-level regional structure is evident from the occurrence of isolation-by-distance patterns among populations, the recognition of clusters of genetically similar, geographically adjacent populations by ordination analysis, and the detection of a substantial mtDNA discontinuity between Argentina and Brazil that coincides with a previously identified landform of biogeographic relevance, the Mesopotamia floodplain. Multiple lines of evidence from both genomes suggest that the ancestors of the ants we studied resembled extant northern Argentine S. invicta, and that existing Brazilian populations were established more recently by serial long-distance colonizations and/or range expansions. The most compelling evidence for this is the corresponding increase in FK (a measure of divergence from a hypothetical ancestor) and decrease in genetic diversity with distance from the Corrientes population in northern Argentina. Relatively deep sequence divergence among several mtDNA clades (as much as 5.1%), coupled with geographic partitioning of many of these clades, suggests a long history of occupation of South America by S. invicta in more-or-less isolated regional populations. Such populations appear, in some cases, to have come into secondary contact without regaining the capacity to freely interbreed. These results lead us to conclude that nominal S. invicta in its native range comprises multiple entities that are sufficiently genetically isolated and diverged to have embarked on independent evolutionary paths.