TABLE 1

Fitness of ancestral clones of populations where their fitness relative to one another deviates from 1

			Relative fitness, W			Regression Ara⁺/Ara⁻ trajectory (day 0–6)
Ara⁺/Ara⁻	Log (Ara⁺/Ara⁻)	Population	Ara⁺vs. Ara⁻clone	Ara⁺ clone vs.Ara⁻ ancestor	Ara⁻ clone vs. Ara⁺ ancestor	Slope,generation⁻¹	P-value
mut⁺/mut⁺	2	1	0.9886*	0.9928	0.9726	−0.01738	0.1265
mut⁺/mut⁺	−1	2	0.9838*	0.9754	1.0082*^a	−0.00271	0.0517
mutS/mut⁺	0	1	0.9933*	0.9725	0.9681	0.00074	0.7823
mutS/mut⁺	0	4	0.9534**	0.9298*	0.9875	−0.01627	0.0026
mutS/mut⁺	−1	1	0.9751*	0.9544*	0.9756	−0.01011	0.0136
mutS/mut⁺	−1	2	1.0140***	1.0039	0.9883	0.00288	0.5244
mutS/mut⁺	−1	4	1.0279**	1.0308*	0.9796	0.01035	0.0296
mutS/mut⁺	−1	6	1.0288*	1.0209*	0.9764	0.00667	0.0051
mutS/mut⁺	−2	3	0.9923	0.9745**	0.9689	0.00392	0.5295
mutS/mut⁺	−3	1	0.9677**	0.9529	0.9954	−0.01175	0.0194
mutS/mut⁺	−3	4	1.0280**	1.0142	0.9651***	0.02108	0.0891
mutS/mut⁺	−3	6	1.0063*	0.9825	0.9950	0.00858	0.3708
mutS/mut⁺	−4	5	1.0101*	0.9890	1.0011	−0.00361	0.3470
mutS/mut⁺	−4	6	1.0076*	0.9963	0.9805	−0.00136	0.7475

Significant negative values indicate deleterious mutations and positive values indicate beneficial mutations in the ancestral background of the subpopulation involved. Asterisks (*) indicate significant deviations from W = 1 on the basis of a two-tailed t-test with d.f. = 2: *P < 0.05, **P < 0.01, ***P < 0.001. The single fitness value in italics is significant at the 0.05 level after correcting for multiple testing (Rice 1989). Underlining indicates those ancestral clones for which competition and regression results consistently indicate the presence of a mutation.
^aAlthough the t-test suggests that the Ara⁻ subpopulation started with a beneficial mutation, both the more extreme (negative) deviation from unity of the Ara⁺ ancestor (which is not significant due to low statistical power, given only three replicate fitness values) and the presumed much higher rate of deleterious relative to beneficial mutations makes this interpretation ambiguous.