Statistical Analyses of Pattern Variation in the Copper-bellied (Nerodia Erythrogaster Neglecta) and Yellow-bellied (N. E. Flavigaster) Watersnake Subspecies

ABSTRACT We conducted a statistical evaluation of the pattern characteristics used to distinguish juvenile and adult copper-bellied (Nerodia erythrogaster neglecta) and yellow-bellied (Nerodia erythrogaster flavigaster) watersnakes. A total of 405 preserved museum specimens (juvenile = 242; adult = 163) was grouped as either neglecta, flavigaster or intermediate based on previous evaluations of the geographical variations of pattern seen in these taxa. Depending on the nature of the character, its state was either scored across its phenotypic range or measured using digital image analysis techniques. The juvenile neglecta and flavigaster phenotypes are consistent with their historical descriptions and the intermediate phenotype is nearly identical to neglecta. The amount and intensity of the dorsal pigment invasion of the ventral scales was the most informative adult charter. Digital image analyses of these characters are consistent with their historical descriptions for the neglecta and flavigaster pheno...