Genome evolution of asexual organisms and the paradox of sex in eukaryotes

Elvira Hörandl*, Jens Bast, Alexander Brandt, Stefan Scheu, Christoph Bleidorn, Mathilde Cordellier, Minou Nowrousian, Dominik Begerow, Anja Sturm, Koen Verhoeven, Jens Boenigk, Thomas Friedl, Micah Dunthorn

*Corresponding author for this work

Research output: Chapter in book/volumeChapterScientificpeer-review

19 Citations (Scopus)
12 Downloads (Pure)

Abstract

The predominance of sex in eukaryotes is still enigmatic. Sex, a composed process of meiosis and mixis cycles, confers high costs but the selective advantages remain unclear. In this review, we focus on potentially detrimental effects of asexuality on genome evolution. Theory predicts that asexual lineages should suffer from lack of meiotic DNA repair, accumulation of deleterious mutations, proliferation of transposable elements, among others. Here, we compare the different genomic features, life cycles, developmental pathways, and cytological mechanisms in the major eukaryotic groups, i.e., in protists, animals, fungi, and plants. In general, it is difficult to disentangle lineage-specific features from general features of asexuality. In all groups, forms of asexuality are predominantly facultative or cyclical. A variety of mixed or partial sexual developmental pathways exists, maintaining some components of sexuality, while obligate asexuality appears to be rare in eukaryotes. The strongest theoretical prediction for negative consequences of asexuality is decreased effectiveness of selection compared to sexuality. While some studies have shown increased rates of mutation accumulation in asexuals, others using whole-genome comparisons did not find this pattern. Various mechanisms exist that can alleviate the negative consequences of accumulation of negative mutations. More empirical data are needed to understand comprehensively the role of genome evolution for the maintenance of sex.

Original languageEnglish
Title of host publicationEvolutionary Biology-A Transdisciplinary Approach
PublisherSpringer
Pages133-167
Number of pages35
ISBN (Electronic)9783030572464
ISBN (Print)9783030572457
DOIs
Publication statusPublished - 29 Oct 2020

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