The evolution of desaturase genes in ants

Territorial behaviors can be advantageous in social organisms, but necessarily depend on processes for differentiating between group members and non-group members. Among many ant species, this process of perceiving and responding to differences in species and colony is mainly governed by an ant's ability to recognize given cuticular hydrocarbon (CHC) profiles. Until now, however, no genes have been identified or isolated that are known to influence the CHC patterns of any social insect; previous research on Drosophila, however, demonstrates that three Δ9/Δ11 desaturase genes, desat1, desat2, and desatF (syn. Fad2), play an important role both in CHC alkene biosynthesis and variability, as they function in mate recognition. In our study of seven ant species, five produced distinct sets of alkenes within their CHC profiles, indicating that the same desaturase genes associated with mate recognition in Drosophila are also viable genome query candidates for study of CHC alkene genes and, therefore, colony/species recognition in ants. Results from our analyses of these seven ant genomes and seven outgroup insects show the presence of five clades of Δ9/Δ11 desaturase genes, with ant gene number conservation in two clades (clade E, CG15531, and clade D, CG9743), losses in one clade (clade C, desatC), and moderate to large expansions among two clades (clade B, CG9747, and clade A, CG8630/desat1). These results suggest that relatively larger expansions of Δ9/Δ11 desaturase genes in ants may be useful in contributing to qualitative and quantitative differences in CHC alkene variation, and show promise as candidates for future studies of ant CHC profiles and recognition cues.