Sex enhances adaptation by unlinking beneficial from detrimental mutations in experimental yeast populations

Gray, Jeremy C. and Goddard, Matthew R. (2012) Sex enhances adaptation by unlinking beneficial from detrimental mutations in experimental yeast populations. BMC Evolutionary Biology, 12 (43). ISSN 1471-2148

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Sex enhances adaptation by unlinking beneficial from detrimental mutations in experimental yeast populations
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Background: The maintenance of sexuality is a classic problem in evolutionary biology because it is a less efficient mode of reproduction compared with asexuality; however, many organisms are sexual. Theoretical work suggests sex facilitates natural selection, and experimental data support this. However, there are fewer experimental studies that have attempted to determine the mechanisms underlying the advantage of sex. Two main classes of hypotheses have been proposed to explain its advantage: detrimental mutation clearance and beneficial mutation accumulation. Here we attempt to experimentally differentiate between these two classes by evolving Saccharomyces cerevisiae populations that differ only in their ability to undergo sex, and also manipulate mutation rate. We cannot manipulate the types of mutation that occur, but instead propagate populations in both stressful and permissive environments and assume that the extent of detrimental mutation clearance and beneficial mutation incorporation differs between them. Results: After 300 mitotic generations interspersed with 11 rounds of sex we found there was no change or difference in fitness between sexuals and asexuals propagated in the permissive environment, regardless of mutation rate. Sex conferred a greater extent of adaptation in the stressful environment, and wild-type and elevated mutation rate sexual populations adapted equivalently. However, the asexual populations with an elevated mutation rate appeared more retarded in their extent of adaptation compared to asexual wild-type populations. Conclusions: Sex provided no advantage in the permissive environment where beneficial mutations were rare. We could not evaluate if sex functioned to clear detrimental mutations more effectively or not here as no additional fitness load was observed in the mutator populations. However, in the stressful environment, where detrimental mutations were likely of more consequence, and where beneficial mutations were apparent, sex provided an advantage. In the stressful environment asexuals were increasingly constrained in their extent of adaptation with increasing mutation rate. Sex appeared to facilitate adaptation not just by more rapidly combining beneficial mutations, but also by unlinking beneficial from detrimental mutations: sex allowed selection to operate on both types of mutations more effectively compared to asexual populations. © 2012 Gray and Goddard; licensee BioMed Central Ltd.

Additional Information:This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords:adaptation, environmental stress, evolutionary biology, experimental study, functional role, hypothesis testing, mutation, natural selection, sex role, yeast, Saccharomyces cerevisiae, MSH2 protein, S cerevisiae, protein MSH2, Saccharomyces cerevisiae protein, adaptation, article, asexual reproduction, genetics, molecular evolution, mutation rate, physiology, reproductive fitness, Saccharomyces cerevisiae, Adaptation, Physiological, Evolution, Molecular, Genetic Fitness, MutS Homolog 2 Protein, Reproduction, Asexual, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Subjects:C Biological Sciences > C182 Evolution
Divisions:College of Science > School of Life Sciences
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ID Code:17153
Deposited On:15 May 2015 10:09

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