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

• DOI: 10.21203/rs.2.9135/v1
• Publication Date: 2019-04-12T17:08:47Z
• Authors: Julie Esmeralda B...; Simone Riss; Bette Hecox-Lea; David B. Mark-Welch; Claus-Peter Stelzer
• Keywords: Genome size; Brachionus calyciflorus; Repeated sequence; Interspersed repeat; GC-content

Abstract Background The causes and consequences of genome size variation across Eukaryotes, which spans five orders magnitude, have been hotly debated since before the advent sequencing. Previous studies mostly examined among larger taxonomic units (e.g., orders, or genera), while comparisons closely related species are rare. Rotifers Brachionus plicatilis complex exhibit a seven-fold in thus represent unique opportunity to study such changes on relatively short evolutionary timescale. Here, we sequenced analysed genomes four this with nuclear DNA contents spanning 110- 422 Mbp. To establish likely mechanisms change, both sequencing read libraries assemblies for signatures polyploidy repetitive element content. We also compared these that B. calyciflorus, closest relative (293 Mbp content). Results summary Despite very large differences size, saw no evidence ploidy level complex. However, content explained portion (at least 54%). largest genome, asplanchnoidis, has strikingly high 44% content, smaller contain between 14% 25% elements. According our analyses, calyciflorus contains 39% elements, is substantially higher than previously reported (21%), suggests load could be widespread monogonont rotifers. Conclusions Even though sizes at low end Metazoan spectrum, their substantial amounts Polyploidy does not appear play role variations species, can by This contradicts naïve expectation small streamlined, less complex, due polyploidy.