Data from: Genetic drift and selection in many-allele range expansions

We experimentally and numerically investigate the evolutionary dynamics of four competing strains of E. coli with differing expansion velocities in radially expanding colonies. We compare experimental measurements of the average fraction, correlation functions between strains, and the relative rates of genetic domain wall annihilations and coalescences to simulations modeling the population as a one-dimensional ring of annihilating and coalescing random walkers with deterministic biases due to selection. The simulations reveal that the evolutionary dynamics can be collapsed onto master curves governed by three essential parameters: (1) an expansion length beyond which selection dominates over genetic drift; (2) a characteristic angular correlation describing the size of genetic domains; and (3) a dimensionless constant quantifying the interplay between a colony’s curvature at the frontier and its selection length scale. We measure these parameters with a new technique that precisely measures small selective differences between spatially competing strains and show that our simulations accurately predict the dynamics without additional fitting. Our results suggest that the random walk model can act as a useful predictive tool for describing the evolutionary dynamics of range expansions composed of an arbitrary number of genotypes with different fitnesses.

我们通过实验与数值模拟手段，研究了径向扩张菌落中四种具有不同扩张速率的大肠杆菌（E. coli）竞争菌株的进化动力学。我们将菌株平均占比、菌株间相关函数，以及遗传域壁湮灭与合并的相对速率的实验测量结果，与将种群建模为一维环上带有选择确定性偏置的湮灭-合并随机行走者的模拟结果进行对比。模拟结果表明，该进化动力学可归拢至由三个核心参数支配的主曲线上：（1）扩张长度——当超过该长度时，选择作用将凌驾于遗传漂变之上；（2）表征遗传域大小的特征角相关量；（3）无量纲常数，用于量化菌落前沿曲率与其选择长度尺度之间的相互作用。我们通过一种可精准测量空间竞争菌株间微小选择差异的新技术测定上述参数，并证明我们的模拟无需额外拟合即可准确预测该进化动力学过程。本研究结果显示，随机行走模型可作为实用的预测工具，用于描述由任意数量具有不同适应度的基因型构成的范围扩张过程的进化动力学。