Metacommunity structure preserves genome diversity in the presence of gene-specific selective sweeps under moderate rates of horizontal gene transfer
Fig 2
In absence of HGT, an infinite-allele model provides a diversity-maintenance mechanism with an intrinsic time scale.
A. We consider a standard neutral model maintaining diversity. At each time step, corresponding to a basic migration-sweep time scale each patch can be swept neutrally by a new species, with an innovation event taking place with rate ν (per patch, per time step), or alternatively, its species can migrate and sweep, invading another patch (and sweeping neutrally), with a rate 1 − ν. Panel B shows diversity (S(t), defined as the total number of distinct species present in the metacommunity at a given time t) in a typical simulation. Diversity relaxes to a plateau, in agreement with (Eq 1). The parameters of the simulation are ν = 0.01 and M = 10 000. C. Comparison between Eq 1 (valid in the limit M ≫ 1 and ν ≪ 1) and simulated data for the equilibrium value of the diversity, plotted as a function of the innovation rate (ν). Simulations correspond to M = 10 000 and averages over 100 independent realizations. For each simulated value of ν the distribution of diversity S is shown as a box plot (blue line: mean value, box: inter-quartile range, fences: max and min values) D. Characterization of the equilibration time scale for the average trajectories of the diversity. The plot shows diversity (scaled by its equilibrium value) vs time, scaled by the common equilibration time scale N/ν. Simulations were performed over 100 independent realizations, for different values of the innovation rate ν (shown in the legend, coded by color and symbol). All the simulations were initialized with a metacommunity of a single species (S(t = 0) = 1).