Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Swiss Institute of Bioinformatics, Lausanne, Switzerland.
J Hered. 2021 Mar 12;112(1):19-33. doi: 10.1093/jhered/esaa031.
Evolution without sex is predicted to impact genomes in numerous ways. Case studies of individual parthenogenetic animals have reported peculiar genomic features that were suggested to be caused by their mode of reproduction, including high heterozygosity, a high abundance of horizontally acquired genes, a low transposable element load, or the presence of palindromes. We systematically characterized these genomic features in published genomes of 26 parthenogenetic animals representing at least 18 independent transitions to asexuality. Surprisingly, not a single feature was systematically replicated across a majority of these transitions, suggesting that previously reported patterns were lineage-specific rather than illustrating the general consequences of parthenogenesis. We found that only parthenogens of hybrid origin were characterized by high heterozygosity levels. Parthenogens that were not of hybrid origin appeared to be largely homozygous, independent of the cellular mechanism underlying parthenogenesis. Overall, despite the importance of recombination rate variation for the evolution of sexual animal genomes, the genome-wide absence of recombination does not appear to have had the dramatic effects which are expected from classical theoretical models. The reasons for this are probably a combination of lineage-specific patterns, the impact of the origin of parthenogenesis, and a survivorship bias of parthenogenetic lineages.
没有性的进化预计会以多种方式影响基因组。对个别孤雌生殖动物的案例研究报告了一些特殊的基因组特征，这些特征被认为是由它们的繁殖方式引起的，包括高杂合度、大量水平获得的基因、低转座元件负荷或回文结构的存在。我们系统地描述了 26 种孤雌生殖动物的已发表基因组中的这些基因组特征，这些动物至少代表了 18 个独立的无性繁殖转变。令人惊讶的是，这些转变中的大多数并没有系统地复制出任何单一的特征，这表明以前报告的模式是特定于谱系的，而不是说明孤雌生殖的一般后果。我们发现，只有杂种起源的孤雌生殖动物具有高水平的杂合度。而不是孤雌生殖起源的孤雌生殖动物似乎主要是纯合的，而与孤雌生殖的细胞机制无关。总的来说，尽管重组率的变化对有性动物基因组的进化很重要，但基因组范围内缺乏重组似乎并没有像经典理论模型所预期的那样产生巨大的影响。造成这种情况的原因可能是谱系特异性模式、孤雌生殖起源的影响以及孤雌生殖谱系的生存偏差的综合作用。
