Department of Biology, University of North Carolina, Chapel Hill, North Carolina, USA.
J Evol Biol. 2022 Jan;35(1):23-39. doi: 10.1111/jeb.13968. Epub 2021 Dec 11.
It is theoretically established that self-fertilization can facilitate mutation accumulation, thus increasing extinction risk. However, in previous studies, selfing rates are often set as fixed parameters, but in natural systems, evolution of selfing rates and deleterious mutations may mutually affect each other. I carried out simulations to investigate the dynamics of selfing rates and mutation accumulation, by allowing deleterious mutations to coevolve with alleles that modify the selfing rate (selfing modifiers). I found that selfing rates will often fluctuate over time, due to successive invasion of alleles that increase selfing and outcrossing. Since mutation fixation is mainly caused by Muller's ratchet, its rate is sensitive to the change of the selfing rate mutations will accumulate in a punctuated pattern. The dynamics are influenced by several factors, such as recombination and the selfing rate effects of selfing modifier loci. Also, such temporal variation produces variation of selfing rates and mutation accumulation rates between multiple conspecific populations, which can increase the average fitness across populations. As factors, such as the genomic mutation rate of deleterious mutations, can simultaneously influence the selfing rate and mutation fixation, effects of these factors on mutation accumulation rates can be complicated and non-monotonic.
理论上认为，自交可以促进突变积累，从而增加灭绝风险。然而，在以前的研究中，自交率通常被设定为固定参数，但在自然系统中，自交率和有害突变的进化可能相互影响。我通过允许有害突变与改变自交率的等位基因（自交修饰基因）共同进化，进行了模拟来研究自交率和突变积累的动态。我发现，由于增加自交和异交的等位基因的连续入侵，自交率通常会随时间波动。由于突变固定主要是由 Muller 的棘轮引起的，因此其速率对自交率变化敏感，突变将以间断的方式积累。这些动态受到几个因素的影响，如重组和自交修饰基因座的自交率效应。此外，这种时间变化会在多个同种群体之间产生自交率和突变积累率的变化，从而增加种群间的平均适应性。由于有害突变的基因组突变率等因素可以同时影响自交率和突变固定，因此这些因素对突变积累率的影响可能是复杂的，且非单调的。
