CPC results and bootstrap distributions for five statistics to compare Littorina data covariance matrices in comparisons within sample (grey-lined boxplots; 1 to 3, Rbs; 4 to 6, Sus), between locations within morph (black-lined boxplots; 7 to 9, between Rbs; 10 to 12, between Sus) and between morphs (grey-filled boxplots; 13 to 18, between morphs of different locations; 19 to 21, between morphs of the same location). The T% values were divided by 100 to make them comparable with the other statistics. The CPC box shows the number of common principal components; U: unrelated. No CPC analysis was done for the comparisons within samples. Plots do not include outliers. Circles mark the observed values for the statistics. No observed values are printed in the case of within sample comparisons (i.e., of matrices with themselves) because they were always equal to one for the RS and equal to zero for the other statistics. Comparison codes: 1, Rb1-Rb1; 2, Rb2-Rb2; 3, Rb3-Rb3; 4, Su1-Su1; 5, Su2-Su2; 6, Su3-Su3; 7, Rb1-Rb2; 8 Rb1-Rb3; 9, Rb2-Rb3; 10, Su1-Su2; 11, Su1-Su3; 12, Su2-Su3; 13, Rb1-Su2; 14, Rb2-Su1; 15, Rb1-Su3; 16, Rb3-Su1; 17, Rb2-Su3; 18, Rb3-Su2; 19, Rb1-Su1; 20, Rb2-Su2; 21, Rb3-Su3.