Results

Figure (1)

Figure (1) shows the frequency of Littorina obtusata's shell color morph distribution upon Ascophyllum nodosum and rock substrata.  The frequency of color distributions was calculated as the fraction of each color morph from the total number of individuals found on the substrate (88 for Ascophyllum and 28 for rock substrate). 
    Dark shell morphs accounted for almost 40% of snails found on Ascophyllum while green morphs constituted about 37.5% and yellow morphs about 22.7%.
    On rock surfaces, dark morphs were approximately 57% of the total individuals, green morphs 39.3%, and yellow only 3.6%.
    Based on the Chi-Square Contingency test, there is a significant (non random) relationship between color and substrate (p = 0.02586).  The hypothesis is supported in that there are proportionately more dark color morphs on rock substrate, and proportionately more yellow color morphs predominate on Ascophyllum nodosum.

Click here for raw color/substrate data

Figure 2

Figure (2) shows the mean height and length in millimeters of the different color morphs.  A single factor analysis of variance (ANOVA) was performed separately for both height and length.  Neither height nor length were related to color morph- p values being 0.36667 and 0.43728 respectively.  Thus, the hypothesis that the mean dimensions of the color morphs would differ among color morphs was not supported.  This is easily confirmed by a visual assessment of Figure (2).

Click here for ANOVA summaries