Figure 6.

Bi-stability: a strong founder effect. (a) A person is infected with a two-point resistant virus that is less fit than a wild-type but recombination prevents reversion to wild-type virus. Parameters are as in figure 5. This situation can equally be thought of as a person infected with wild-type virus with recombination preventing the emergence of fitter resistant strains. (b) The steady-state gene frequency p_ab is plotted as a function of fitness f_ab, illustrating the two coexisting equilibria for intermediate values of f_ab (plotted in black). The analytical approximation of equation (A 17) is also plotted (thick red line), showing excellent agreement, even when f_ab>1.