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Deleterious mutation accumulation in asexual Timema stick insects.
Lee Henry1, Tanja Schwander, Bernard J Crespi
1Zoology Department, University of Oxford, Oxford, United Kingdom.
Molecular Biology and Evolution
|September 24, 2011
Summary
Sexual reproduction helps purge harmful mutations, unlike asexual reproduction. This study found significantly higher mutation rates in asexual stick insects, limiting their long-term survival.
Area of Science:
- Evolutionary biology
- Genetics
- Molecular evolution
Background:
- Sexual reproduction is prevalent despite its costs, suggesting significant evolutionary advantages.
- Asexual reproduction may lead to the accumulation of deleterious mutations, shortening evolutionary lifespan.
- The purging of mildly deleterious mutations is a key hypothesized benefit of sexual reproduction.
Purpose of the Study:
- To investigate the rate of coding mutation accumulation in asexual versus sexual lineages.
- To determine if asexual lineages accumulate deleterious mutations at a higher rate than sexual lineages.
- To assess the impact of these mutations on the long-term persistence of asexual lineages.
Main Methods:
- Analysis of coding (nonsynonymous) mutations in mitochondrial (COI) and nuclear (Actin, Hsp70) genes.
- Comparison of mutation accumulation rates in six asexual Timema stick insect lineages and related sexual species.
- Evaluation of the functional impact of mutations based on amino acid hydrophobicity changes.
Main Results:
- Significantly higher rates of coding mutation accumulation (3.6- to 13.4-fold) were observed in all six asexual Timema lineages compared to sexual species.
- Mutations in asexual lineages often caused substantial changes in amino acid hydrophobicity, suggesting more deleterious effects.
- Evidence of increased mutation accumulation was found across all three analyzed genes.
Conclusions:
- Deleterious mutation accumulation rates differ significantly between sexual and asexual lineages.
- The accumulation of harmful mutations likely plays a crucial role in limiting the long-term evolutionary persistence of all-female lineages.
- These findings support the hypothesis that sex facilitates the purging of deleterious mutations, conferring a long-term evolutionary advantage.
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