Conclusions

Overall, we did not find any consistent patterns linking CHC profile variation, CHC biosynthesis transcriptome diversity, and social complexity across the seven Blattodea species included in our study. This is partially reflective of the results Kather and Martin (2015) obtained in their meta-analysis of solitary and eusocial Hymenopteran CHC diversity, although this study was lacking the genetic component. This implies that, at least for our representative species spanning different levels of social complexity within the order Blattodea, neither their CHC profiles nor their repertoire of CHC biosynthesis gene transcripts does reflect any social hierarchy or correlate with their social complexity. Concerning the genetic background of CHC biosynthesis, however, it must be taken into account that our general knowledge remains limited and mostly biased towards Drosophila(Holze et al. 2021), so it is quite possible that more Blattodea-specific CHC biosynthesis genes exist which have not been functionally characterized yet and have therefore eluded our comprehensive gene transcript investigation. Nevertheless, our study challenges the long-standing assumption of a general correlation between increasing social complexity and chemical profile sophistication for our Blattodea study species. Therefore, we strongly suggest more cautious approaches for assessing, comparing, and interpreting chemical complexity in insects with different levels of social organization.

Tables

Tab 1 : List of 21 genes with a demonstrated function in the CHC biosynthesis pathway for which we could detect transcripts in at least one of our tested cockroach and termite species. The numbers correspond to the position of the respective gene product in the biosynthesis pathway (compare to Fig. 1). Gene acronyms, (putative) functions, NCBI (or Genbank when not available in NCBI) IDs and the taxon where the gene was originally described are indicated along with the detected copy numbers in our tested species. The CHC biosynthesis genes were retrieved from Holze et al. (2021).