Effects of a single gene on worker and male body mass in the fire ant Solenopsis invicta (Hymenoptera : Formicidae)

This study examines the effects of general-protein-9 (Gp-9) genotype on the body mass of polygyne (multiple-queens per nest) Solenopsis invicta Buren workers and males. We found that Gp-9 genotype was significantly associated with variation in worker mass in field but not laboratory colonies. Moreov er, triploid workers with 2 distinguishable genotypes (Gp-9(BBb) and Gp-9(B bb)) weighed significantly more than diploid workers with the heterozygous genotype (Gp-9(Bb)). Our results, combined with those obtained from previou s studies, indicate that Gp-9 genotype, ploidy, social form, and colony que en number affect mass of S. invicta workers. We also discovered that Gp-9 g enotype significantly influenced the mass of haploid males reared in both f ield and laboratory environments. As a group, polygyne males were significa ntly lighter than monogyne males, even when Gp-9 genotype was taken into ac count, indicating that social environment interacts with Gp-9 genotype to i nfluence male mass. Given that diploid males previously have been shown to be lighter than haploid males, 3 factors (Gp-9 genotype, social form, and p loidy) are now known to affect the mass of male fire ants.