|Vander Meer, Robert - Bob|
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2006
Publication Date: 5/1/2006
Citation: Fritz, G.N., Vander Meer, R.K., Preston, C.A. 2006. Selective Male Mortality in the Red Imported Fire Ant, Solenopsis invicta. Genetics. 173: 207-213. Interpretive Summary: The social organization of fire ants is very complex and depends to a large extent on the breeding system of the ant. Understanding this system is necessary to exploit this vulnerable part of the fire ant’s biology. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida, and the Department of Biological Sciences at Eastern Illinois University at Charleston, Illinois, examined the breeding system of multiple-queen colonies of fire ant by genotyping queens, their stored sperm, and males for a gene thought to code for a pheromone-binding protein affecting complex social behavior. We discovered for the first time that multiple mating of fire ant female sexuals occurs. Our results also led to the proposal that a pattern of differential mortality of two genetically defined sexual types in colonies may depend on worker genetic type frequencies. This selective mortality of male and female sexuals, in turn, is predicted to affect multiple aspects of the breeding system including female-mediated dispersal, mating success, and gene-flow. This information will be useful in planning future, targeted fire ant control research.
Technical Abstract: Our understanding of social insect organization and the forces that shape interactions fundamentally relies on our understanding of breeding systems and how these affect genetic structure and flow. The breeding system of multiple-queen colonies of the Red Imported Fire Ant was examined by genotyping queens, their stored sperm, and males for a gene (the Gp-9 locus) believed to code for a pheromone-binding protein affecting complex social behavior. Samples were taken from four sites with different proportions of both social forms (monogyne and polygyne colonies) in sympatry. Four colonies from one site were also profiled for Gp-9 by sampling sexuals, workers and brood. Most queens were heterozygotes and primarily mated by B males. Increases in the frequency of polygyne colonies paralleled increases in the frequency of queens mated by males of their own social form and of non-inseminated queens. Queens mated to polygyne males ranged from 1.9% to 32.8% at four sites. The presence of both B and b sperm in 1.9% to 13.3% of queens, genotype profiles of colonies, and genotypes of offspring from individual queens are consistent with some degree of multiple-mating. Genetic profiles of males and of four colonies at one site show that the bb genotype is not an obligate recessive lethal, but that selective mortality (probably culling by workers) is directed at certain genotypes of both male and female sexuals early in development. We propose that the pattern of differential mortality of sexual genotypes in colonies may depend on worker genotype frequencies. Selective mortality of sexuals, in turn, is predicted to affect multiple aspects of the breeding system including female-mediated dispersal, mating success, and gene flow.