Sugar alcohol concentrations in C. aculeata and D. muscorum samples representing experimental and control groups (square = mean, box = SE, whisker = 95% confidence interval, n = 8): a ribitol concentration, b arabitol concentration, and c mannitol concentration. The different letters above the bars indicate significant differences (p < 0.05). Lowercase letters indicate a significant interaction, capital letters indicate the significant effect of lichen species. The asterisk indicates a significant effect of the experimental group. For details see Suppl. material 1: table S1.