Influence Of Factors On The Mutation Rate In Asexual Populations

In any natural populations, mutation is the primary source of genetic variation required for evolutionary novelty and adaptation. Nevertheless, most mutations, especially those with phenotypic effects, are harmful and removed by natural selection. Therefore, the mutation rate, which reflects the number of mutations, is an important parameter in organism evolution. In most cases, an organism can evolve to a lower mutation rate under relentless selection. Then, which factors are related to selection on the mutation rate?In order to answer this question, we use stochastic simulations to design the process of organism evolution, where considering many factors which influence the mutation rate. Besides, we discussed the relative impact of those factors. This study is based on a high level, which considers the competition among subpopulations firstly, to investigate how natural selection adjusts the optimum mutation rate. Given a particular mutation rate to each subpopulation, those 10 subpopulations can compete with one another. The mutation rate of the"winner"subpopulation is defined as"the optimum mutation rate". When conditions of population change, the optimum mutation rate may vary.We obtained major results based on the competition among subpopulations as follows.1, Among many factors which influence the optimum mutation rate, both population size and the mutation effects are most importance.2, The larger a population is, the higher the optimum mutation rate of the population could evolve to.3, Population could evolve to a higher mutation rate with increasing the fraction of beneficial mutations.4, Population favors a much higher mutation rate with increasing the effects of beneficial mutations. Contrary to the significant impact by varying beneficial mutations effects, deleterious mutations contributed little to the optimum mutation rate.It should be noticed that strong favored mutations had also surprisingly impact on the generation needed in competitions, which was rare to be observed in comparison to varying other parameters.We hope the method developed here and these findings above might prove good explanations on the lower mutation rates in most asexual organisms and higher mutation rate in some virus.