Table 1 Parameters included in each model used for estimating the DFE

Model	S_d	b	S_b	p_b	r_i	ε_anc	θ
0	Fitted	Fitted	Fitted	Fitted	1	0	Fitted
1	Fitted	Fitted	Fitted	Fitted	Fitted	0	Fitted
2	Fitted	Fitted	Fitted	Fitted	Fitted	Fitted	Fitted
3	Fitted	Fitted	0	0	Fitted	0	Fitted
4	Fitted	Fitted	0	0	Fitted	Fitted	Fitted

In gray are the two models on which most of our results are based. S_d is the mean population scaled selection coefficient of new additive deleterious mutations (s ≤ 0), b is the shape parameter of the deleterious DFE, S_b is the mean population scaled selection coefficient of new additive beneficial mutations, p_b is the proportion of new beneficial mutations (s > 0), r_i is the series of nuisance parameters used to control for potential distorters of the uSFS, ε_anc is the polarization error, and θ is the population scaled mutation rate (4N_eμ).