Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA.
PLoS One. 2013 Jul 17;8(7):e68179. doi: 10.1371/journal.pone.0068179. Print 2013.
Replicators such as parasites invading a new host species, species invading a new ecological niche, or cancer cells invading a new tissue often must mutate to adapt to a new environment. It is often argued that a higher mutation rate will favor evolutionary invasion and escape from extinction. However, most mutations are deleterious, and even lethal. We study the probability that the lineage will survive and invade successfully as a function of the mutation rate when both the initial strain and an adaptive mutant strain are threatened by lethal mutations. We show that mutations are beneficial, i.e. a non-zero mutation rate increases survival compared to the limit of no mutations, if in the no-mutation limit the survival probability of the initial strain is smaller than the average survival probability of the strains which are one mutation away. The mutation rate that maximizes survival depends on the characteristics of both the initial strain and the adaptive mutant, but if one strain is closer to the threshold governing survival then its properties will have greater influence. These conclusions are robust for more realistic or mechanistic depictions of the fitness landscapes such as a more detailed viral life history, or non-lethal deleterious mutations.
复制因子（如侵入新宿主物种的寄生虫、侵入新生态位的物种、或侵入新组织的癌细胞）通常必须通过突变来适应新环境。人们常认为，较高的突变率有利于进化入侵和避免灭绝。然而，大多数突变是有害的，甚至是致命的。我们研究了当初始菌株和适应性突变菌株都受到致命突变的威胁时，作为突变率的函数，谱系存活和成功入侵的概率。我们表明，如果在无突变极限下，初始菌株的生存概率小于距离一个突变的菌株的平均生存概率，那么突变是有益的，即非零突变率会增加生存概率。使生存最大化的突变率取决于初始菌株和适应性突变菌株的特征，但如果一个菌株更接近生存的阈值，那么它的特性将产生更大的影响。这些结论对于更现实或更具体的适应景观（如更详细的病毒生活史或非致命性有害突变）具有稳健性。
