Satellite DNA (satDNA) is an abundant class of tandemly repeated noncoding sequences, showing high rate of change in sequence, abundance, and physical location. However, the mechanisms promoting these changes are still controversial. The library model was put forward to explain the conservation of some satDNAs for long periods, predicting that related species share a common collection of satDNAs, which mostly experience quantitative changes. Here, we tested the library model by analyzing three satDNAs in ten species of Schistocerca grasshoppers. This group represents a valuable material because it diversified during the last 7.9 Myr across the American continent from the African desert locust (Schistocerca gregaria), and this thus illuminates the direction of evolutionary changes. By combining bioinformatic and cytogenetic, we tested whether these three satDNA families found in S. gregaria are also present in nine American species, and whether differential gains and/or losses have occurred in the lineages. We found that the three satDNAs are present in all species but display remarkable interspecies differences in their abundance and sequences while being highly consistent with genus phylogeny. The number of chromosomal loci where satDNA is present was also consistent with phylogeny for two satDNA families but not for the other. Our results suggest eminently chance events for satDNA evolution. Several evolutionary trends clearly imply either massive amplifications or contractions, thus closely fitting the library model prediction that changes are mostly quantitative. Finally, we found that satDNA amplifications or contractions may influence the evolution of monomer consensus sequences and by chance playing a major role in driftlike dynamics.

中文翻译：

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Schistocerca属蝗虫中八百万年的卫星DNA进化阐明了图书馆假说的来龙去脉。

卫星DNA（satDNA）是一类丰富的串联重复非编码序列，显示序列，丰度和物理位置的变化率很高。但是，促进这些变化的机制仍存在争议。提出了该库模型来解释某些satDNA的长期保存，并预测相关物种具有共同的satDNA集合，其中大部分经历了定量变化。在这里，我们通过十个品种分析3个satDNAs测试的库模型蝗蚱蜢。这个群体代表了一种有价值的物质，因为在整个美洲大陆的最后7.9迈尔期间，它从非洲沙漠蝗虫（Schistocerca gregaria）），从而阐明了进化变化的方向。通过结合生物信息学和细胞遗传学，我们测试了这三个satDNA家族是否存在于S. gregaria中在9个美洲物种中也都存在它们，以及谱系中是否出现了不同的收益和/或损失。我们发现三个satDNAs存在于所有物种中，但在它们的丰度和序列上显示出明显的种间差异，同时与系统发生属高度一致。存在satDNA的染色体基因座的数量也与两个satDNA家族的系统发育一致，而与另一个不相同。我们的结果表明，satDNA进化的重大偶然事件。几个进化趋势显然暗示着大规模的扩增或收缩，因此与拟合的库模型预测非常吻合，即预测大多数是定量的。最后，