Amir’s study of the odorant receptors (ORs) on the fire ant social chromosome was published in Genome Biology and Evolution:

We discovered a cluster of 23 ORs in the supergene that determines the social form of Solenopsis invicta colonies. Many of these genes are the results of recent duplications in the fire ant lineage. Most strikingly, two of them were deleted in the Sb haplotype (th variant found in polygyne colonies). This is the most dramatic mutation discovered to date, which differentiates the Sb and the SB haplotypes. This makes these genes great candidates for explaining the difference between the two social forms, especially the discrimination of queen genotypes based on olfactory cues.