Predicted reduction in divergence rates at sites that are under selection in nuclear genes of C. elegans due to Muller's ratchet. The black dashed lines indicate the effects of variability in Ne (1000 – 100 000). The histogram shows observed KA/KS values between C. elegans and C. briggsae, suggesting that observed divergence is roughly compatible with most selection coefficients having effects between about 0.1 and 0.0001. The inferred rate of fixation of deleterious mutations relative to the rate for neutral mutations is computed by dividing 1/Usdm by the predicted effective click time (parameters as in Figure 1).
Loewe and Cutter BMC Evolutionary Biology 2008 8:125 doi:10.1186/1471-2148-8-125