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Kočí J, Röslein J, Pačes J, Kotusz J, Halačka K, Koščo J, Fedorčák J, Iakovenko N, Janko K. No evidence for accumulation of deleterious mutations and fitness degradation in clonal fish hybrids: Abandoning sex without regrets. Mol Ecol 2020; 29:3038-3055. [PMID: 32627290 PMCID: PMC7540418 DOI: 10.1111/mec.15539] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/18/2020] [Accepted: 06/22/2020] [Indexed: 02/07/2023]
Abstract
Despite its inherent costs, sexual reproduction is ubiquitous in nature, and the mechanisms to protect it from a competitive displacement by asexuality remain unclear. Popular mutation-based explanations, like the Muller's ratchet and the Kondrashov's hatchet, assume that purifying selection may not halt the accumulation of deleterious mutations in the nonrecombining genomes, ultimately leading to their degeneration. However, empirical evidence is scarce and it remains particularly unclear whether mutational degradation proceeds fast enough to ensure the decay of clonal organisms and to prevent them from outcompeting their sexual counterparts. To test this hypothesis, we jointly analysed the exome sequences and the fitness-related phenotypic traits of the sexually reproducing fish species and their clonal hybrids, whose evolutionary ages ranged from F1 generations to 300 ky. As expected, mutations tended to accumulate in the clonal genomes in a time-dependent manner. However, contrary to the predictions, we found no trend towards increased nonsynonymity of mutations acquired by clones, nor higher radicality of their amino acid substitutions. Moreover, there was no evidence for fitness degeneration in the old clones compared with that in the younger ones. In summary, although an efficacy of purifying selection may still be reduced in the asexual genomes, our data indicate that its efficiency is not drastically decreased. Even the oldest investigated clone was found to be too young to suffer fitness consequences from a mutation accumulation. This suggests that mechanisms other than mutation accumulation may be needed to explain the competitive advantage of sex in the short term.
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Affiliation(s)
- Jan Kočí
- Department of Biology and Ecology, University of Ostrava, Ostrava, Czechia.,Institute of Animal Physiology and Genetics, Czech Academy of Science, Liběchov, Czechia
| | - Jan Röslein
- Department of Biology and Ecology, University of Ostrava, Ostrava, Czechia.,Institute of Animal Physiology and Genetics, Czech Academy of Science, Liběchov, Czechia
| | - Jan Pačes
- Institute of Animal Physiology and Genetics, Czech Academy of Science, Liběchov, Czechia.,Institute of Molecular Genetics, Czech Academy of Science, Prague, Czechia
| | - Jan Kotusz
- Museum of Natural History, University of Wrocław, Wrocław, Poland
| | - Karel Halačka
- Institute of Vertebrate Biology, Czech Academy of Science, Brno, Czechia
| | - Ján Koščo
- Department of Ecology, University of Prešov, Prešov, Slovakia
| | - Jakub Fedorčák
- Department of Ecology, University of Prešov, Prešov, Slovakia
| | - Nataliia Iakovenko
- Department of Biology and Ecology, University of Ostrava, Ostrava, Czechia.,Institute of Animal Physiology and Genetics, Czech Academy of Science, Liběchov, Czechia
| | - Karel Janko
- Department of Biology and Ecology, University of Ostrava, Ostrava, Czechia.,Institute of Animal Physiology and Genetics, Czech Academy of Science, Liběchov, Czechia
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