Originally published as Genetics Published Articles Ahead of Print on February 19, 2006.

Genetics, Vol. 173, 207-213, May 2006, Copyright © 2006
doi:10.1534/genetics.106.056358

Selective Male Mortality in the Red Imported Fire Ant, Solenopsis invicta

Gary N. Fritz*,1, Robert K. Vander Meer{dagger} and Catherine A. Preston{dagger}

* Department of Biological Sciences, Eastern Illinois University, Charleston, Illinois 61920 and {dagger} Center for Medical, Agricultural, and Veterinary Entomology, USDA Agricultural Research Service, Gainesville, Florida 32608

1 Corresponding author: Eastern Illinois University, Department of Biological Sciences, 600 Lincoln Ave., Charleston, IL 61920. 
E-mail: cfgnf{at}eiu.edu

Males in polygyne populations of Solenopsis invicta are primarily sterile diploids and thought to not express the Gp-9 gene coding for a pheromone-binding protein affecting complex social behavior. We examined an aspect of the breeding system hitherto not considered—male Gp-9 genotypes in relation to sperm stored in queens. Four sites with varying frequencies of sympatric monogyne and polygyne colonies were sampled, including sexuals, workers, and broods from four colonies. Most queens were heterozygotes storing B sperm. Although predicted to be common, only 14 of 504 males were B or BB genotypes, suggesting strong selection. Increased frequency of polygyne colonies at each site paralleled increases in queens with b sperm (1.9–32.8%) and of noninseminated queens. The presence of both B and b sperm in 1.9–18.9% of queens, genotype profiles of colonies, and genotypes of offspring from individual queens suggest some frequency of multiple mating. The bb genotype, rather than an obligate, developmental lethal, was present in some queens and common in alates, workers, and brood. Selective mortality of sexuals may affect multiple aspects of the breeding system, including female-mediated dispersal, mating success, and gene flow.