Stochastic dynamics of three competing clones: conditions and times for invasion, coexistence and fixation

In large clonal populations, several clones generally compete which results in complex evolutionary and ecological dynamics: experiments show successive selective sweeps of favorable mutations as well as long-term coexistence of multiple clonal strains. The mechanisms underlying either coexistence or fixation of several competing strains have rarely been studied altogether. Conditions for coexistence has mostly been studied by population and community ecology, while rates of invasion and fixation have mostly been studied by population genetics. In order to provide a global understanding of the complexity of the dynamics observed in large clonal populations, we develop a stochastic model where three clones compete. Competitive interactions can be intransitive and we suppose that strains enter the population via mutations or rare immigrations. We first describe all possible final states of the population, including stable coexistence of two or three strains, or the fixation of a single st...在大型克隆种群（clonal population）中，多个克隆类群通常会发生竞争，进而催生复杂的演化与生态动力学过程：实验研究表明，有利突变会经历连续的选择性清扫（selective sweep）事件，同时伴随多种克隆菌株（clonal strains）的长期共存现象。目前，针对多种竞争菌株共存与固定背后的潜在机制，鲜有研究能够全面统筹解析。其中，共存条件的相关研究多由种群与群落生态学领域主导，而入侵与固定速率的探讨则主要隶属于群体遗传学范畴。为了全面理解大型克隆种群中观测到的动力学复杂性，我们构建了一个包含三个竞争克隆类群的随机模型（stochastic model）。该模型中的竞争相互作用可具备非传递性（intransitive competition），同时我们假定菌株可通过突变或罕见的迁入事件进入种群。我们首先描述了该种群所有可能的最终状态，其中包括两株或三株菌株的稳定共存，或是单株菌株的固定……