Pairwise head shape comparisons among subspecies within the Western Rattlesnake (Crotalus viridis) complex.

Pairwise subspecific shape differences (i.e., Procrustes distances) are arrayed below the diagonal, whereas P-values that stem from 10,000 random permutations of data are above the diagonal. The single non-significant Procrustes distance (i.e., cerberus versus abyssus) is depicted in bold, as is its corresponding P-value. Values in bold italics represent Procrustes distance comparisons among the three sister-taxa (i.e., lutosus/ abyssus; helleri/ calignis; viridis/ nuntius), with corresponding P-values in bold blue as well.