Sociality in weevils is shaped by sheltering and convergent gene losses

Eusociality, a complex social structure featuring shared parental care, cooperative reproduction, and labor division, has evolved separately multiple times in different insect groups, including weevils. While previous research has examined the genetic basis of social behavior in Hymenoptera (ants, bees, wasps) and Blattodea (termites), the evolutionary changes underlying sociality in weevils remain largely unexplored.

Weevils (Curculionidae) offer a unique opportunity to study this phenomenon, as they exhibit a range of social systems, from simple parental care to the exclusive eusocial species, Austroplatypus incompertus.

In a recent study, researchers sequenced the genomes of A. incompertus and two facultatively eusocial weevil species, Xylosandrus germanus and Xyleborinus saxesenii. By comparing these genomes with those of 18 other weevil species, the team identified genetic signatures of social evolution. Their results suggest that the transition to eusociality in weevils is marked by relaxed purifying selection and a decrease in gene family sizes, particularly in A. incompertus.

This pattern of "relaxed selection and gene loss" is a departure from the more complex genetic mechanisms seen in other eusocial insects. The findings support the idea that reduced population sizes and increased sheltering may have played key roles in the evolution of sociality in weevils, a trend not previously documented in other insect groups.