Metacommunity structure preserves genome diversity in the presence of gene-specific selective sweeps under moderate rates of horizontal gene transfer
Fig 3
In presence of HGT only, and no diversity-maintenance mechanism, the fixation of a beneficial gene in the metacommunity can lead to a moderate loss of diversity.
A. A beneficial gene can spread across patches (i) via migration events (reducing diversity) or (ii) via HGT-sweep (maintaining diversity) The two processes take place at each time step, with rate pm (per patch, per time step) and ph (per patch, per time step) respectively. Here, we assume that no diversity-maintenance mechanism counteracts the diversity loss (this assumption will be relaxed later) B. Simulations of this model show a diversity (S(t)) loss from the initial value (Si) to a new stable value (Sf), corresponding to complete invasion of the beneficial gene. Each solid line is a realization, with initial condition of the simulations generated by the neutral model described in Fig 2 (M = 10000 and ν = 0.02), and with parameters ph = 0.2 and pm = 1 − ph. C-D. Comparison between analytical prediction (Eq 3) and simulated data for the sweep parameter Q = 〈Sf/Si〉 as a function of the ratio ph/pm (panel C, ν = 0.01), and of the innovation rate of the neutral model generating the initial diversity (panel D, ph = 0.1, pm = 0.9). Simulations performed with M = 10 000. The panels CD show the distribution of diversity S over 100 realizations as a box plot (blue line: mean value, box: inter-quartile range, fences: max and min values).