PUB - Publikationen an der Universität Bielefeld

Eukaryotic organisms vary widely in genome size and much of this variation can be explained by differences in the abundance of repetitive elements. However, the phylogenetic distributions and turnover rates of repetitive elements are largely unknown, particularly for species with large genomes. We therefore used de novo repeat identification based on low coverage whole-genome sequencing to characterize the repeatomes of six species of gomphocerine grasshoppers, an insect clade characterised by unusually large and variable genome sizes. Genome sizes of the six species ranged from 8.4 to 14.0pg DNA per haploid genome and thus include the second largest insect genome documented so far (with the largest being another acridid grasshopper). Estimated repeat content ranged from 79 to 96% and was strongly correlated with genome size. Averaged over species, these grasshopper repeatomes comprised significant amounts of DNA transposons (24%), LINE elements (21%), helitrons (13%), LTR retrotransposons (12%) and satellite DNA (8.5%). The contribution of satellite DNA was particularly variable (ranging from <1% to 33%) as was the contribution of helitrons (ranging from 7 to 20%). The age distribution of divergence within clusters was unimodal with peaks around 4-6%. The phylogenetic distribution of repetitive elements was suggestive of an expansion of satellite DNA in the lineages leading to the two species with the largest genomes. Although speculative at this stage, we suggest that the expansion of satellite DNA could be secondary and might possibly have been favoured by selection as a means of stabilising greatly expanded genomes. © The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.