Dynamics of chromosome evolution in termites: Inbreeding, novel chromosomal translocations, and sociality

Termites are diploid eusocial roaches with an XY sex-determination system compared to their ancestors, cockroaches, with an XO sex-determination system. Chromosomal rearrangements play an important role in the evolution of sex chromosomes and altering the genomic patterns on a population scale. An interesting chromosomal feature in reproduction that is still not well studied, is the presence of ring chromosomal chains in male meiosis which have been theoretically associated with inbreeding. These multivariate chains comprise different numbers of chromosomes that vary between and within species. Studies on other eusocial insects postulate inbreeding plays a positive evolutionary role by facilitating kin selection. However, in termites, inbreeding and ring chromosome formation have only been discussed from a theoretical population genetic standpoint. Hence, using European species of the genus Reticulitermes as our study system, we give insight into the link between ring chromosome formation and sex chromosome evolution at the origin of termite eusociality. Further, we investigate the evolutionary causes and consequences of ring chromosome formation at the population level. To achieve this, we use chromosome-level assemblies from males of the ring and non-ring chromosome-forming species. Comparative and population genomics analyses will assess the extent of divergence between populations and within species. De-novo assembly and annotation of the putative Y-chromosome have been done using archival datasets. Further, comparative analyses between termite and cockroach species using whole genome alignment have shown the existence of synteny and differences indicative of structural variations.