BACKGROUND AND AIMS Changes in the amount of repetitive DNA (dispersed and tandem repeats) are considered the main contributors to genome size variation across plant species in the absence of polyploidy. However, the study of repeatome dynamism in groups showing contrasting genomic features and complex evolutionary histories is needed to find out whether other processes underlying genome size variation have been largely overlooked. The main aim was to elucidate which mechanism better explains GS evolution in Anacyclus (Asteraceae). METHODS Using data from Illumina sequencing, we analysed the repetitive DNA in all species of Anacyclus, a genus with a reticulate evolutionary history, which displays significant genome size and karyotype diversity albeit presenting a stable chromosome number. KEY RESULTS By reconstructing ancestral genome size values, we inferred independent episodes of genome size expansions and contractions during the evolution of the genus. However, the analysis of the repeatome revealed a similar DNA repeat composition across species, both qualitative and quantitative. Using comparative methods to study repeatome dynamics in the genus, we found no evidence for repeat activity causing genome size variation among species. CONCLUSIONS Our results, combined with previous cytogenetic data, suggest that genome size differences in Anacyclus are more likely related to chromosome rearrangements involving losses or gains of chromosome fragments, possibly associated with homoploid hybridisation. These could represent balanced rearrangements that do not disrupt gene dosage in merged genomes, e.g., via chromosome segment exchanges.

中文翻译：

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恒定染色体数目下的基因组大小变化与 Anacyclus（菊科）中的重复 DNA 动态无关

背景和目的 在没有多倍体的情况下，重复 DNA（分散和串联重复）数量的变化被认为是导致植物物种间基因组大小变化的主要因素。然而，需要对显示对比基因组特征和复杂进化历史的群体中的重复组动态进行研究，以找出基因组大小变异背后的其他过程是否在很大程度上被忽视了。主要目的是阐明哪种机制可以更好地解释 Anacyclus（菊科）中的 GS 进化。方法使用 Illumina 测序的数据，我们分析了 Anacyclus 的所有物种中的重复 DNA，该属具有网状进化历史，尽管染色体数量稳定，但显示出显着的基因组大小和核型多样性。主要结果 通过重建祖先基因组大小值，我们推断出该属进化过程中基因组大小扩张和收缩的独立事件。然而，重复组的分析揭示了跨物种的相似 DNA 重复组成，无论是定性还是定量。使用比较方法研究该属中的重复组动态，我们没有发现重复活动导致物种间基因组大小变化的证据。结论 我们的结果与之前的细胞遗传学数据相结合，表明 Anacyclus 的基因组大小差异更可能与涉及染色体片段丢失或增加的染色体重排有关，可能与同倍体杂交有关。这些可能代表不破坏合并基因组中基因剂量的平衡重排，例如，通过染色体片段交换。