Queen Dispersal Strategies in the Multiple-Queen Form of the Fire Ant Solenopsis invicta

Newly produced queens in the multiple-queen (polygyne) form of the fire ant Solenopsis invicta show dramatic variation in dispersal patterns, and this variation is influenced by genotypic variation at a single locus associated with the genetic marker Gp-9. Heavy, homozygous Gp-9 queens exhibit the highest vagility among polygyne queens and are strongly attracted to the open, disturbed-habitat patches that characteristically attract queens of the single-queen (monogyne) form (all of which possess genotype Gp9). Intermediate weight, heterozygous Gp-9 queens exhibit a mixed dispersal strategy: some remain in the area near their natal nest, while others disperse to land in the same disturbed-habitat patches as Gp-9 queens. Light, homozygous Gp-9 queens appear to lack the energy reserves needed to take part in mating flights in substantial numbers. Most queens that disperse from their natal nest site apparently fail to infiltrate mature nests to reproduce. However, consistent with the expectations of game-theoretical models for the evolution of dispersal, the low realized success of dispersing queens does not prevent relatively large numbers of them from dispersing. Furthermore, the results presented here are consistent with the hypothesis that the reproductive syndrome that characterizes polygyny in S. invicta is largely controlled by a single locus.