| Abstract: | Published data on mean rates of genetic divergence for a substantial number of protein molecules is used to examine the hypothetical effect of variations in these rates upon the expected relationship between evolutionary time and Nei's (1972, American Naturalist, 106: 283) genetic distance, D. Results indicate that at higher values D can be expected to deviate significantly from stochastic linearity with time. However, over the sort of time scale over which D values are normally estimated, deviation is slight and likely to be insignificant when compared to other potential sources of error. It is concluded that for most practical purposes interprotein differences in mean rates of amino acid substitution need not be taken into account when calibrating genetic distance estimates against evolutionary time. |
