Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, 230 Castetter Hall, MSC03-2020, Albuquerque, NM 87131, USA.
J R Soc Interface. 2013 May 29;10(85):20130329. doi: 10.1098/rsif.2013.0329. Print 2013 Aug 6.
When mutation rates are low, natural selection remains effective, and increasing the mutation rate can give rise to an increase in adaptation rate. When mutation rates are high to begin with, however, increasing the mutation rate may have a detrimental effect because of the overwhelming presence of deleterious mutations. Indeed, if mutation rates are high enough: (i) adaptive evolution may be neutralized, resulting in a zero (or negative) adaptation rate despite the continued availability of adaptive and/or compensatory mutations, or (ii) natural selection may be neutralized, because the fitness of lineages bearing adaptive and/or compensatory mutations--whether established or newly arising--is eroded by excessive mutation, causing such lineages to decline in frequency. We apply these two criteria to a standard model of asexual adaptive evolution and derive mathematical expressions--some new, some old in new guise--delineating the mutation rates under which either adaptive evolution or natural selection is neutralized. The expressions are simple and require no a priori knowledge of organism- and/or environment-specific parameters. Our discussion connects these results to each other and to previous theory, showing convergence or equivalence of the different results in most cases.
当突变率较低时，自然选择仍然有效，增加突变率会导致适应率的增加。然而，如果突变率一开始就很高，增加突变率可能会产生不利影响，因为有害突变的压倒性存在。事实上，如果突变率足够高：（i）适应性进化可能会被中和，导致适应率为零（或负），尽管适应性和/或补偿性突变仍然存在，或（ii）自然选择可能会被中和，因为携带适应性和/或补偿性突变的谱系的适合度——无论是已经建立的还是新出现的——被过度突变侵蚀，导致这些谱系的频率下降。我们将这两个标准应用于无性适应进化的标准模型，并推导出数学表达式——一些是新的，一些是以新的形式出现的旧的——来描述适应性进化或自然选择被中和的突变率。这些表达式简单，不需要事先了解生物体和/或环境特定参数的知识。我们的讨论将这些结果相互联系起来，并与以前的理论联系起来，在大多数情况下，不同结果的收敛或等效性。
