(Epi)Genetic Mechanisms Underlying the Evolutionary Success of Eusocial Insects

SIMPLE SUMMARY: Social insects, namely ants, bees, and termites, are among the most numerous and successful animals on Earth. This is due to a variety of features: highly cooperative behavior performed by colony members and their specialization on a variety of tasks. Diverse physiological and behavioral specializations are regulated not only by the genetic system, but also by the epigenetic system which alters gene expressions without modifying the genetic code. This review will summarize recent advancements in such studies in eusocial insects. ABSTRACT: Eusocial insects, such as bees, ants, and wasps of the Hymenoptera and termites of the Blattodea, are able to generate remarkable diversity in morphology and behavior despite being genetically uniform within a colony. Most eusocial insect species display caste structures in which reproductive ability is possessed by a single or a few queens while all other colony members act as workers. However, in some species, caste structure is somewhat plastic, and individuals may switch from one caste or behavioral phenotype to another in response to certain environmental cues. As different castes normally share a common genetic background, it is believed that much of this observed within-colony diversity results from transcriptional differences between individuals. This suggests that epigenetic mechanisms, featured by modified gene expression without changing genes themselves, may play an important role in eusocial insects. Indeed, epigenetic mechanisms such as DNA methylation, histone modifications and non-coding RNAs, have been shown to influence eusocial insects in multiple aspects, along with typical genetic regulation. This review summarizes the most recent findings regarding such mechanisms and their diverse roles in eusocial insects.