Population genomics of sexual and asexual lineages in fissiparous ribbon worms (Lineus, Nemertea): hybridization, polyploidy and the Meselson effect
Population genomics of sexual and asexual lineages in fissiparous ribbon worms (Lineus, Nemertea): hybridization, polyploidy and the Meselson effect
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DOI：
10.1111/mec.13717
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发表时间：
2016-07-01
影响因子：
4.9
通讯作者：
Galtier, N.
中科院分区：
文献类型：
--
作者：
Ament-Velasquez, S. L.;Figuet, E.;Galtier, N.
无性与有性物种的比较群体遗传学提供了研究无性对基因组进化的影响的机会。在这里，我们分析编码序列多态性和分歧模式的迷人的线带状蠕虫，一组海洋，肉食性纽虫与不寻常的再生能力，并在其中无性生殖fissiparity记录。对裂殖吸虫的群体基因组进行了研究。pseudolacteus的特征在于极高水平的杂合性和出乎意料地升高的pi（N）/pi（S）比率，与克隆进化下的理论预期明显一致。然而，对两个物种的等位基因共享和读数分布的分析表明，L。pseudolacteus是L. sanguineus和L. lacteus。我们模拟和量化的相对影响杂交，多倍体和无性系的分子变异模式在L。pseudolacteus的特征，并得出结论：（i）L. pseudolacteus群体基因组学的结果在第一位的杂交和（ii）通过Meselson效应的新突变的积累是超过补偿的杂合性侵蚀的过程，如基因转换或基因拷贝丢失。这项研究说明了与无性恋相关的进化过程的复杂性，并确定了L。pseudolacteus作为一个有前途的模型，研究多倍体基因组进化的第一步，在无性环境。
Comparative population genetics in asexual vs. sexual species offers the opportunity to investigate the impact of asexuality on genome evolution. Here, we analyse coding sequence polymorphism and divergence patterns in the fascinating Lineus ribbon worms, a group of marine, carnivorous nemerteans with unusual regeneration abilities, and in which asexual reproduction by fissiparity is documented. The population genomics of the fissiparous L. pseudolacteus is characterized by an extremely high level of heterozygosity and unexpectedly elevated pi(N)/pi(S) ratio, in apparent agreement with theoretical expectations under clonal evolution. Analysis of among-species allele sharing and read-count distribution, however, reveals that L. pseudolacteus is a triploid hybrid between Atlantic populations of L. sanguineus and L. lacteus. We model and quantify the relative impact of hybridity, polyploidy and asexuality on molecular variation patterns in L. pseudolacteus and conclude that (i) the peculiarities of L. pseudolacteus population genomics result in the first place from hybridization and (ii) the accumulation of new mutations through the Meselson effect is more than compensated by processes of heterozygosity erosion, such as gene conversion or gene copy loss. This study illustrates the complexity of the evolutionary processes associated with asexuality and identifies L. pseudolacteus as a promising model to study the first steps of polyploid genome evolution in an asexual context.