Annotated genome assemblies for Geoscapheus dilatatus, Panesthia cribrata and Neogeoscapheus hanni

Genetic changes that enabled the evolution of eusociality have long
captivated biologists. More recently, attention has focussed on the
consequences of eusociality on genome evolution. Studies have reported
higher molecular evolutionary rates in eusocial hymenopteran insects
compared with their solitary relatives. To investigate the genomic
consequences of eusociality in termites, we analysed nine genomes,
including newly sequenced genomes from three non-eusocial cockroaches.
Using a phylogenomic approach, we found that termite genomes have
experienced lower rates of synonymous substitutions than those of
cockroaches, possibly as a result of longer generation times. We
identified higher rates of non-synonymous substitutions in termite genomes
than in cockroach genomes, and identified pervasive relaxed selection in
the former (24–31% of the genes analysed) compared with the latter (2–4%).
We infer that this is due to reductions in effective population size,
rather than gene-specific effects (e.g. indirect selection of caste-biased
genes). We found no obvious signature of increased genetic load in
termites, and postulate efficient purging of deleterious alleles at the
colony level. Additionally, we identified genomic adaptations that may
underpin caste differentiation, such as genes involved in
post-translational modifications. Our results provide insights into the
evolution of termites and the genomic consequences of eusociality more
broadly.