Fitness of complex isoforms across different growth conditions. Expected fitness effects upon deletion of a random gene of whole isoforms across the two fermentable and the three non-fermentable media considered. The fitness values are partitioned into four categories: 'strong negative effect' (--/blue), 'moderate negative effect' (-/light-blue), 'weak or no effect' (0/white) and 'positive effect' (+/orange). Each line represents the fitness profile of a given isoform. 'n/a': the expected fitness effect is unknown due to a lack of quantitative fitness information for the genes in the respective isoform. When grouping the fitness profiles, we gave priority to n/a, positive, strong negative and moderate negative fitness effect in that order. Arrows indicate isoform fitness profiles of complexes given as examples in the main text.