Relative fitness ln(v) in pairwise competitions between BC, PA wild type and PA cheat in iron-limited CAA medium across three different spatial structures. BC is outcompeted by the PA wild type at all spatial structures (a). The PA cheat is a weaker competitor than the PA wild type, but still significantly outcompetes BC at all spatial structures (b). The PA wild type is outcompeted by the PA cheat only under low spatial structure (c). The relative fitness ln(v) of the focal strain (the first strain in the panel headers) is shown for three levels of spatial structure (square=low, circle=intermediate, triangle=high), and was calculated after 24 h of competition. The values of ln(v)<0, ln(v)>0, or ln(v)=0, indicate whether the focal strain respectively lost, won, or performed equally well in competition with its opponent. Gray symbols represent individual data points, whereas black symbols indicate means±95% CI. Asterisks indicate significant differences between treatments (*P<0.05, **P<0.01, ***P<0.001).