Table 3 . Expected deviations from additivity on r (ε).

Model	Expected ε
Additive on λ	ln(λwt + mν) − n ln(1 + ν/λwt)
Multiplicative on λ	0
Stickbreaking on λ	ln[(λwt + d − d(1 − ν)m] − rwt − m ln(1 + dν/λwt)
Additive on r	0
Multiplicative on r	rwt (1 + ν)m − rwt (1 + mν)
Stickbreaking on r	d − d(1 − ν)m − mdν

ε is defined as r_obs − r_pred. The left column gives the model under which data arise while the right column gives the expected value of ε as a function of the number of fixed mutations (m) and the mean intrinsic effect of mutations that fix (ν).