Johann-Friedrich-Blumenbach Institute of Zoology and Anthropology, University of Goettingen, 37073 Goettingen, Germany;
Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland.
Proc Natl Acad Sci U S A. 2021 Sep 21;118(38). doi: 10.1073/pnas.2101485118.
Sex strongly impacts genome evolution via recombination and segregation. In the absence of these processes, haplotypes within lineages of diploid organisms are predicted to accumulate mutations independently of each other and diverge over time. This so-called "Meselson effect" is regarded as a strong indicator of the long-term evolution under obligate asexuality. Here, we present genomic and transcriptomic data of three populations of the asexual oribatid mite species and its sexual relative We document strikingly different patterns of haplotype divergence between the two species, strongly supporting Meselson effect-like evolution and long-term asexuality in : I) variation within individuals exceeds variation between populations in but vice versa in ; II) two sublineages feature a high proportion of lineage-specific heterozygous single-nucleotide polymorphisms (SNPs), indicating that haplotypes continued to diverge after lineage separation; III) the deepest split in gene trees generally separates the two haplotypes in , but populations in ; and IV) the topologies of the two haplotype trees match each other. Our findings provide positive evidence for the absence of canonical sex over evolutionary time in and suggest that asexual oribatid mites can escape the dead-end fate usually associated with asexual lineages.
性通过重组和分离强烈影响基因组进化。在没有这些过程的情况下，预测二倍体生物谱系内的单倍型将独立于彼此积累突变并随时间推移而分化。这种所谓的“Meselson 效应”被认为是强制性无性长期进化的强烈指标。在这里，我们展示了三种有性或无脊椎螨物种 和其有性近缘种 的基因组和转录组数据。我们记录了这两个物种之间单倍型分化的截然不同模式，强烈支持类似于 Meselson 效应的进化和 在 中存在长期无性繁殖：I）个体内的变异超过种群间的变异，但 在 中则相反；II）两个 亚谱系具有高比例的谱系特异性杂合单核苷酸多态性（SNP），表明单倍型在谱系分离后仍继续分化；III）基因树中最深的分裂通常将 的两个单倍型分开，但 在 中的种群则不然；和 IV）两个单倍型树的拓扑结构相互匹配。我们的研究结果为 在进化时间内不存在典型性别的情况提供了积极证据，并表明无脊椎螨可以逃脱与无性谱系相关的死胡同命运。
