Population genetics study of the imported fire ants (Formicidae: Solenopsis spp.)

The study was divided into three main sections. In the first section, temporal stability of genetic structure of red imported fire ant populations and effective population sizes were assessed with the help of microsatellites. The second part of the study was focused on the development of new microsatellite markers for the population genetics study of fire ants. The third part of the study was aimed at describing the association of phenotypic and genotypic characters of polygyne hybrid (Solenopsis invicta x richteri) fire ant in a colony and identifying the origin of polygyny in hybrid imported fire ant colony. Meridian, Yazoo City and Crystal Springs in Mississippi and Mobile, Alabama were selected for conducting the study. The overall FST estimates and the pairwise FST estimates between the populations of study, indicated little genetic differentiation and low spatial variation in the nuclear genetic structure of red imported fire ant. Gene flow estimates indicated that there is extensive movement between these populations. From 2006 to 2008 the FST estimates decreased and gene flow estimates increased, indicating that there is no equilibrium between genetic drift and migration in the populations studied. Effective population sizes ranged from 10 -17 in these populations.We have isolated and characterized an additional 11 polymorphic microsatellite loci in the invasive ant S. invicta from a population in Lauderdale County, Mississippi. The observed and effective number of alleles ranged from two to six (average 3.1818 ± S. E. 0.0486). Probability tests indicated significant deviations from the Hardy-Weinberg equilibrium at three loci. The polymorphism information content of the microsatellites ranged from 0.1482 to 0.6208.Identifying multiple inseminated queens in a colony and sequencing the critical region of Gp-9 locus (1600 base pairs) in individuals with the polygyne allele strongly indicate the association of phenotypic and genotypic characters of polygyny in a hybrid imported fire ant colony. A 100% match of Gp-9B and Gp-9b alleles and concordance in the critical amino acid substitutions of the Gp-9 locus in the hybrid fire ant with S. invicta Buren provides the evidence that polygyny in the hybrid imported fire ant colony is derived from S. invicta