Affiliations: 1) Indiana University Bloomington; 2) University of California Berkeley
Keywords: Comparative genomics & genome evolution
Beetles are the most species-rich group of animals and harbor diverse karyotypes. Most species have XY sex chromosomes, but X0 sex determination mechanisms are also common in some groups. We generate whole-chromosome assemblies of two beetle species and utilize eight additional beetle genomes to reconstruct karyotype evolution across Coleoptera. We identify ancestral linkage groups that share a conserved set of genes across beetles, thereby revealing chromosome conservation over hundreds of millions of years. While the ancestral X chromosome is maintained across beetles, we find distinct cases of additions of autosomes to the ancestral sex chromosomes. These neo-sex chromosomes evolve the stereotypical properties of sex chromosomes, including the evolution of dosage compensation, and genes with sex-biased expression. Beetles thus provide a novel model to gain a better understanding of the diverse forces driving sex chromosome evolution and we propose a standardized chromosome naming scheme aimed at helping future studies of genome evolution within this exceptionally diverse radiation.