Department of Biology, University of Virginia, Charlottesville, Virginia 22904, USA.
Evolution. 2010 Apr 1;64(4):1129-35. doi: 10.1111/j.1558-5646.2009.00869.x. Epub 2009 Oct 23.
Evolutionary theory suggests that low mutation rates should favor the persistence of asexuals. Additionally, given the observation that most nonneutral mutations are deleterious, asexuality may strengthen selection for reduced mutation rates. This reciprocal relationship raises the possibility of a positive feedback loop between sex and mutation rate. We explored the consequences of this evolutionary feedback with an individual-based model in which a sexual population is continually challenged by the introduction of asexual clones. We found that asexuals were more likely to spread in a population when mutation rates were able to evolve relative to a model in which mutation rates were held constant. In fact, under evolving mutation rates, asexuals were able to spread to fixation even when sexuals faced no cost of sex whatsoever. The added success of asexuals was the result of their ability to evolve lower mutation rates and thereby slow the process of mutation accumulation that otherwise limited their spread. Given the existence of ample mutation rate variation in natural populations, our findings show that the evolutionary feedback between sex and mutation rate may intensify the "paradox of sex," supporting the argument that deleterious mutation accumulation alone is likely insufficient to overcome the reproductive advantage of asexual competitors in the short term.
进化理论表明，低突变率应该有利于无性生殖的持续存在。此外，鉴于大多数非中性突变是有害的这一观察结果，无性生殖可能会加强对降低突变率的选择。这种相互关系提出了性和突变率之间存在正反馈循环的可能性。我们使用基于个体的模型来探索这种进化反馈的后果，其中一个有性种群不断受到引入无性克隆的挑战。我们发现，当突变率能够相对于突变率保持不变的模型进化时，无性生殖更容易在种群中传播。事实上，在进化的突变率下，无性生殖甚至可以传播到固定状态，而性生殖根本没有任何性别的代价。无性生殖的额外成功是因为它们能够进化出更低的突变率，从而减缓了否则会限制其传播的突变积累过程。鉴于自然种群中存在大量的突变率变异，我们的研究结果表明，性和突变率之间的进化反馈可能会加剧“性的悖论”，支持这样一种观点，即有害突变的积累本身在短期内可能不足以克服无性生殖竞争者的生殖优势。
