Department of Evolutionary Theory, Max Planck Institute for Evolutionary Biology, 24306 Plön, Germany.
Proc Natl Acad Sci U S A. 2022 Sep 13;119(37):e2205424119. doi: 10.1073/pnas.2205424119. Epub 2022 Sep 6.
Evolutionary dynamics on graphs has remarkable features: For example, it has been shown that amplifiers of selection exist that-compared to an unstructured population-increase the fixation probability of advantageous mutations, while they decrease the fixation probability of disadvantageous mutations. So far, the theoretical literature has focused on the case of a single mutant entering a graph-structured population, asking how the graph affects the probability that a mutant takes over a population and the time until this typically happens. For continuously evolving systems, the more relevant case is that mutants constantly arise in an evolving population. Typically, such mutations occur with a small probability during reproduction events. We thus focus on the low mutation rate limit. The probability distribution for the fitness in this process converges to a steady state at long times. Intuitively, amplifiers of selection are expected to increase the population's mean fitness in the steady state. Similarly, suppressors of selection are expected to decrease the population's mean fitness in the steady state. However, we show that another set of graphs, called suppressors of fixation, can attain the highest population mean fitness. The key reason behind this is their ability to efficiently reject deleterious mutants. This illustrates the importance of the deleterious mutant regime for the long-term evolutionary dynamics, something that seems to have been overlooked in the literature so far.
例如，已经表明存在选择的放大器，与非结构化群体相比，它们会增加有利突变的固定概率，同时降低不利突变的固定概率。到目前为止，理论文献主要集中在单个突变体进入图结构群体的情况，研究图如何影响突变体接管群体的概率以及通常发生这种情况所需的时间。对于不断进化的系统，更相关的情况是突变体在不断进化的群体中不断出现。通常，这种突变在繁殖事件中以较小的概率发生。因此，我们关注低突变率极限。在这个过程中，适应度的概率分布在长时间后收敛到一个稳定状态。直观地，选择的放大器预计会增加稳定状态下群体的平均适应度。同样，选择的抑制剂预计会降低稳定状态下群体的平均适应度。然而，我们表明，另一组称为固定抑制剂的图可以达到最高的群体平均适应度。这背后的关键原因是它们能够有效地拒绝有害突变体。这说明了有害突变体状态对长期进化动力学的重要性，这在迄今为止的文献中似乎被忽视了。
