Figure 1.

Proportions of polymorphic (a) mimetic and (b) non-mimetic colour phenotypes are highly variable across 49 populations of Sonora episcopa in the Great Plains of the USA and northern Mexico. Mimetic colour trait combinations (from left to right, a) include both black crossbands and a red stripe, black crossbands only, a red stripe only and neither crossbands nor red stripe (uniform). Non-mimetic colour trait combinations (from left to right, b) include both a black cap on the head and black nuchal band, a black cap only, a black nuchal band only and neither a cap nor nuchal band. The shade of grey of each population point (detection probability) corresponds to the probability of detecting a rare morph at 5% frequency given the number of individuals sampled in our dataset. See electronic supplementary material, table S1 for population details. (Online version in colour.)