Evolution of odorant receptor repertoires across Hymenoptera is not linked to the evolution of eusociality

Communication is essential for social organisms. In eusocial insects,
olfaction facilitates communication and recognition between nestmates. The
study of certain model organisms has led to the hypothesis that odorant
receptors are expanded in eusocial Hymenoptera. This has become a widely
mentioned idea in the literature, albeit with conflicting reports, and has
not been tested with a broad comparative analysis. Here we combined
existing genomic and new neuroanatomical data, including from a ~100
million-year-old fossil ant, across a phylogenetically broad sample of
hymenopteran lineages. We find no evidence that variation in the size and
evolutionary tempo of odorant receptor repertoires is related to
eusociality. Post-hoc exploration of our data hinted at the loss of flight
as a possible factor shaping some of the variation in OR repertoires in
Hymenoptera. Nevertheless, our analyses revealed a complex pattern of
evolutionary variation and raised new questions about the ecological,
behavioral, and social factors that shape olfactory abilities.