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

Males in polygyne populations of Solenopsis invicta, are primarily sterile diploids and thought not to 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 brood from four colonies. Most queens were heterozygotes storing B sperm. Though 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% to 32.8%) and of non-inseminated queens. The presence of both B and b sperm in 1.9% to 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.

Key Words: Gp-9, Solenopsis invicta, breeding system, polygyne, selection

Online ISS 1091-6490
Copyright 2008 by the Genetics Society of America
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