Genome size, rather than sociality, predicts the turnover of duplicated genes in termites and hymenopterans

Gene duplication is a major source of genetic variation and is considered as an important driver of evolutionary novelties, including eusociality in insects, such as ants, wasps, bees, and termites. However, it remains unclear whether selection acts to increase gene copy number in social insects. Here, we studied the paranomes, namely, the whole set of paralogous genes in a genome, of Blattodea and Hymenoptera. We estimated the rates of gene duplication and loss using the distribution of synonymous substitution rate of paralogous genes and showed that regardless of sociality, duplicated genes were lost more rapidly than expected under random drift, indicating that negative selection on duplicated genes is prevalent across Blattodea and Hymenoptera. The rates of gene duplication and loss varied independently of sociality levels, but were positively related to genome size, suggesting the expansion/contraction of gene families can be a side effect of genome expansion/contraction. These results call for a reevaluation of adaptative gene duplications.