Effects of a Single Gene on Worker and Male Body Mass in the Fire Ant Solenopsis invicta (Hymenoptera: Formicidae)

Abstract

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. Moreover, triploid workers with 2 distinguishable genotypes ( Gp-9BBb and Gp-9Bbb ) weighed significantly more than diploid workers with the heterozygous genotype ( Gp-9Bb ). Our results, combined with those obtained from previous studies, indicate that Gp-9 genotype, ploidy, social form, and colony queen number affect mass of S. invicta workers. We also discovered that Gp-9 genotype significantly influenced the mass of haploid males reared in both field and laboratory environments. As a group, polygyne males were significantly lighter than monogyne males, even when Gp-9 genotype was taken into account, indicating that social environment interacts with Gp-9 genotype to influence male mass. Given that diploid males previously have been shown to be lighter than haploid males, 3 factors ( Gp-9 genotype, social form, and ploidy) are now known to affect the mass of male fire ants.