DFE was determined by competition against gfp reporter strain (Bs175) during exponential phase in complex medium for 4 h. Grey: Control DFE obtained from competition experiments between recipient (Bs166) and gfp reporter strain (grey). A Distribution of selection coefficients s. Arrows denote outliers (large effect transfers) from the distribution derived at a significance level of α = 0.05 after Bonferroni correction. Numbers denote respective strains of BSPIZ. B Mean selection coefficients of core distributions excluding outliers <s^se>. Error bars: confidence intervals obtained from bootstrap analysis. C Standard deviation of selection coefficients of core distributions excluding outliers σ^se. Error bars: confidence intervals obtained from bootstrap analysis.