# Cryptocercus Genomes Expand Knowledge of Adaptations to Xylophagy and Termite Sociality

## TL;DR

This study uses genomes of Cryptocercus cockroaches to explore how wood-eating and social behaviors evolved, revealing new insights into the genetic changes linked to these traits.

## Contribution

The study provides new genomic evidence challenging assumptions about the genetic basis of sociality and xylophagy in Blattodea.

## Key findings

- Relaxed selection is observed in Cryptocercus and termites, suggesting reduced effective population size in subsocial ancestors.
- Cryptocercus shows elevated dN/dS ratios, contradicting the expected correlation with social complexity.
- A shift in methylation patterns and reduction in Ionotropic Receptors occurred in a common ancestor of Cryptocercus and termites.

## Abstract

Subsociality and wood-eating or xylophagy are understood as key drivers in the evolution of eusociality in Blattodea (cockroaches and termites), two features observed in the cockroach genus Cryptocercus, the sister group of all termites. We analyze two high-quality genomes from this genus, C. punctulatus from North America and C. meridianus from Southeast Asia, to explore the evolutionary transitions to xylophagy and subsociality within Blattodea. Our analyses reveal evidence of relaxed selection in both Cryptocercus and termites, indicating that a reduction in effective population size may have occurred in their subsocial ancestors. These findings challenge the expected positive correlation between dN/dS ratios and social complexity, as Cryptocercus exhibits elevated dN/dS values that may exceed those of eusocial termites. Additionally, we infer a reduction in the number of Ionotropic Receptors and a change from uni- to bimodal methylation signatures in protein coding genes in a common ancestor of Cryptocercus and termites, mechanisms previously thought to have evolved with the emergence of eusociality in termites. Future studies incorporating additional genomic data from diverse blattodean species can further build on these findings and provide deeper insights into the molecular mechanisms driving transitions to xylophagy and eusociality.