This work suggests that a relatively small number of genes, many of which are predicted to play a role in chemical communication, determine social organization. This research also increases our understanding of how the social environment can indirectly influence the expression of socially relevant traits.

The fire ant Solenopsis invicta displays natural variation in the number of queens per colony. While the colony-level phenotype results from the aggregation of individuals' behavior, it seems to be regulated by one genomic region marked by the gene Gp-9. This genetic factor also determines whether workers tolerate a single fertile queen (monogene social form) or multiple queens (polygene social form) in their colony.

The current study found that 39 genes are differentially expressed between workers with different Gp-9 genotypes, including several genes likely to regulate chemical signaling and response. The chemical communication mediated by these gene products is essential to the regulation of colony queen number and social organization.

The study also identified 91 genes that are indirectly influenced by the social environment, including Gp-9 genotypes of nest mates, a finding that demonstrates how specific social environments can modulate individual gene expression in group members. This research hints at the genetic complexities likely to be found in other social animals, and represents an important step in the detailed genetic analysis of social behavior.

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Journal Reference:

1. Wang et al. Genome-Wide Expression Patterns and the Genetic Architecture of a Fundamental Social Trait. PLoS Genetics, 2008; 4 (7): e1000127 DOI: 10.1371/journal.pgen.1000127