Figure 3. Principal component plot of shell shape variation for specimens used in this study. The first three principal component (PC) axes explain 75.8% of the total variation in shell shape (PC1 = 57.3%; PC2 = 11.6%; PC3 = 6.9%). (A) Shape variation along PC1 and PC2 with photographs of representative individuals for each species. Scale bars = 1 cm. (B) Shape variation along PC1 and PC3. Species are designated as: Amusium pleuronectes (blue squares), 'Amusium' balloti (blue circles), Argopecten irradians (red squares), Argopecten purpuratus (red circles), Chlamys behringiana (green triangles), Caribachlamys sentis (green diamonds), Pseudamussium septemradiatus (white inverted triangles).