Experimental transitions to selfing result in adaptation. (A) Experimental design. (B) Trioecious populations lost males when cultured at 305 mM NaCl. (C) Dynamics of the selfing allele. Transition fitness was significantly different from zero in the sudden and gradual regimes (both analysis of variance (ANOVA) P-values <0.001, residual d.f. =10). B and C, circles are the observed mean values of replicate populations with error bars one standard mean error among them. (D) Fitness response of trioecious populations after 35 generations of evolution (Δw
). A linear mixed effects model (LMM) shows that populations from all regimes adapted to 305 mM (control test against the zero intercept: |z| =1.76, P-value =0.09; gradual: |z| =2.7, P-value =0.007; sudden: |z| =7.8, P-value <0.001; residual d.f. =65). Post hoc Tukey tests show that sudden populations had a higher fitness response than either gradual or control populations (sudden versus gradual t17 = 2.5, P =0.05; sudden versus control t17 = 2.74, P-value =0.04; gradual versus control t17 = 0.4, P-value =0.9). (E) As panel D, but for monoecious populations. LMM shows a fitness response in 305 mM NaCl by G35 in sudden and gradual populations (control: |z| =0.28, P-value =0.98; gradual: |z| =2.6, P-value =0.009; sudden: |z| =3.8, P-value <0.001; residual d.f. =69; no post hoc differences between regimes). (F), as panels D and E, but for androdioecious populations. LMM shows a fitness response in 305 mM NaCl by G35 in sudden and gradual populations (control: |z| =0.64, P-value =0.52; gradual: |z| =3, P-value =0.003; sudden: |z| =4.9, P-value <0.001; residual d.f. =55; no post hoc differences between regimes). For panels D, E and F, bars and errors show LMM estimates. +, *, **, *** indicate, respectively, P-values of <0.1, <0.05, <0.01 and <0.001. d.f., degrees of freedom.