Fig. 2
From: Discrete or indiscrete? Redefining the colour polymorphism of the land snail Cepaea nemoralis
Axes of chromatic variation in the shell of C. nemoralis, using avian visual space, shown from two different perspectives (see also Supplementary Movie 2). Units on x, y and z axes are in JNDs. The solid lines illustrate variation along the first three principal components; individual points are coloured according to Mclust classification of the shell, either yellow, pink or brown. Top: Variation along PC1 (87%) mainly represents differences in saturation between shells, with some more limited variation in stimulation of L cones. PC2 (11%) shows relatively higher stimulation of L cones and lesser stimulation of M and S cones, and tends to separate brown from pink/yellow. Bottom: PC3 (2%) shows relatively high stimulation of the M cones compared to lesser stimulation of the S and L cones, and tends to separate yellow from pink and pink from brown
