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Genetic drift and selection in many-allele range expansions

Fig 6

Simulations of the average fraction F of a less fit strain and the annihilation asymmetry ΔP collapsed onto universal curves parameterized by .

Two neutral strains swept through a less fit strain with a wall velocity v_w; each strain was numerically inoculated in equal proportions and the colony’s initial radius was R₀. For identical κ, despite different values of R₀ and v_w, both F and ΔP can be collapsed if the length traveled L is rescaled by , the linear selection length scale. Each universal curve at a fixed κ consists of six simulations with different values of v_w and R₀; each set of parameters has a different marker. As κ decreases, inflation slows the selective sweep of the more fit strains through the less fit strain as illustrated by the slower decrease of F. ΔP transitioned from 0 to 1 as the number of strains present in the expansion decreased from q = 3 to q = 2 (the less fit strain was squeezed out); this is expected from eq (3), ΔP = (3 − q)/(q − 1). Supplementary S3 Fig is identical to this figure except the y-axis of F(L/L_s, κ) is placed on a linear scale; this may be useful for comparison with experiments.

doi: https://doi.org/10.1371/journal.pcbi.1005866.g006