No evidence for accumulation of deleterious mutations and fitness
degradation in clonal fish hybrid: Abandoning sex without regrets
- Jan Kočí,
- Jan Röslein,
- Jan Pačes,
- Jan Kotusz,
- Karel Halacka,
- Ján Koščo,
- Jakub Fedorčák,
- Nataliia Iakovenko,
- Karel Janko
Jan Pačes
Institute of Molecular Genetics of the ASCR, v. v. i.
Author ProfileAbstract
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
non-recombining 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 analyzed
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 non-synonymity 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 to that in
the younger ones. In summary, although a purifying selection may still
be relaxed 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.19 Feb 2020Submitted to Molecular Ecology 10 Apr 2020Reviewer(s) Assigned
04 May 2020Review(s) Completed, Editorial Evaluation Pending
05 May 2020Editorial Decision: Revise Minor
18 Jun 2020Review(s) Completed, Editorial Evaluation Pending
18 Jun 20201st Revision Received
22 Jun 2020Editorial Decision: Accept