Evolutionary dynamics of repetitive elements and genome size in Tetrigidae (Orthoptera: Caelifera)

Repetitive elements (REs), involving both satellite DNA (satDNA) and transposable elements (TEs), significantly influence the evolutionary dynamics of the host genome. The order Orthoptera, known for its large genomes, serves as an ideal model for studying the relationship between repeat elements and genome size. We conducted a comparative repeatome analysis across ten Tetrigidae species, using low-coverage short reads in RepeatExplorer2 and dnaPipeTE. Our findings revealed that RE content constitutes between 42.82% (in Thoradonta yunnana) and 60.86% (in Saussurella cornuta) of their genomes, with major components including LINEs, LTR/Gypsy, LTR/Copia, and DNA transposons (Maverick and Helitron). We observed a strong positive correlation between repeat and TE content with genome size, suggesting genome expansion in Tetrigidae is likely driven primarily by repetitive DNA, particularly transposable elements. TE divergence analysis, calculated using RepeatMasker, indicates that species with large genomes, such as S. cornuta (2.836 Gb) and Formosatettix gonggashanensis (1.465 Gb), have experienced both ancient and recent bursts of TE activity. Satellitome analysis revealed a diverse range of satDNA families, with Macromotettixoides jiuwanshanensis having the highest number (34 families) and Phaesticus moniliantennatus showing the greatest abundance (16.76%). Additionally, a fossil-calibrated phylogeny based on 13 mitochondrial protein-coding genes (PCGs) enabled ancestral state reconstructions of genome size, repeat content, and TE composition, revealing lineage-specific patterns of genomic evolution. This study highlights the critical role of repetitive DNA, particularly TEs, in driving genomic complexity and expansion, offering key insights into the evolutionary dynamics of Tetrigidae.