Small, but surprisingly repetitive genomes: Transposon expansion and not polyploidy has driven a doubling in genome size in a metazoan species complex

The causes and consequences of genome size variation across Eukaryotes, which spans five orders of magnitude, have been hotly debated since before the advent of genome sequencing. Previous studies have mostly examined variation among larger taxonomic units (e.g., orders, or genera), while comparisons among closely related species are rare.