Figure 1.
The extent of inbreeding depression as a function of deleterious mutation rate.
Mean inbreeding depression under complete outcrossing (S = 0; solid line) and complete selfing (S = 1; broken line), were obtained analytically for an infinite population (equations 1a, b). The dashed-dotted line shows the threshold level of inbreeding depression ( = 0.5), below which selfing is evolutionarily stable. Selection parameters are set to be h = 0.2 and s = 0.1, based on available data for Drosophila melanogaster [19], [20].
Figure 2.
The rate of mutation accumulation as a function of population size.
For each combination of U ( = 0.1, 0.3, and 0.5) and s ( = 0.01 and 0.1), simulation results are illustrated for populations under complete selfing (S = 1; broken lines), predominant selfing with slight outcrossing (S = 0.97; heavy solid lines), or complete outcrossing (S = 0; thin solid lines). The average rate of mutation accumulation was obtained by taking the arithmetic mean over 1000 generations after the systems reached steady states. Error bars indicate the standard deviations. Throughout, the degree of dominance was h = 0.2. The data points for situations with no fixation (i.e. when the mutation accumulation rate was zero) were omitted from the figure. Note that ordinates are given in (common) logarithmic scale. Note also that the ranges of parameters shown in the two axes vary among panels.
Figure 3.
Comparison of the mutation accumulation rates when deleterious mutation rates vary between mating systems.
Simulation results are illustrated for populations under complete selfing (S = 1; broken lines), predominant selfing with slight outcrossing (S = 0.97; heavy solid lines), or complete outcrossing (S = 0; thin solid lines). The selection coefficient was either s = 0.01 (A, B) or 0.1 (C, D), with h = 0.2 in all cases. Distinct rates of deleterious mutation were assigned to selfing and outcrossing populations, for which appropriate mutation rates were predicted from the analytical model as developed in Text S1. The mutation rate was kept at U = 0.1 (A, C) or 0.3 (B, D) for populations with complete selfing or slight outcrossing, whereas U = 0.5 for completely outcrossing populations. Error bars indicate the standard deviations. Note that ordinates are given in (common) logarithmic scale. The data points for situations with no fixation (i.e. when the mutation accumulation rate was zero) were omitted from the figure. Note also that the range of population size shown in the horizontal axis varies among panels.