A taxonomic investigation of the black ratsnake, Elaphe o. obsoleta (Say) [Reptilia, Squamata, Colubridae], in West Virginia using morphometric analyses

A recent genetic study by Frank T. Burbrink (2000) determined that the common Black Ratsnake, Elaphe o. obsoleta, evolved from three separate evolutionary lineages and can no longer be classified under a single species name. The newly assigned species, which possess ranges that are separated into three regions of the eastern United States by geologic features such as rivers and mountains, are also said to possess distinct morphologic characteristics (Burbrink, 2001). This thesis study was initiated to mirror Burbrink's previous morphometric study and augment a previous lack of specimen data from West Virginia. Black Ratsnake museum specimens, collected from ranges of all three new species, were compared to West Virginia specimens and to Cornsnakes (a statistical outgroup). All specimens were measured for predetermined morphometric characters, including scale counts, scale measurements, and derived characters. Character data were subjected to multivariate statistical tests, including Canonical Discriminant Analysis (CDA), Principal Component Analysis, and Analysis of Variance (ANOVA). A dorsal pattern survey was also performed on Black Ratsnakes (using digital photography) to analyze trends in pattern retention of adult snakes. CDA, PCA, and ANOVA showed little to no significant (P>0.05) separation in Black Ratsnake specimens collected from different geographical areas. Individuals displayed much variation within and among groups. Cornsnake specimens were significantly different (P<0.0001) than Black Ratsnake specimens in all tests. The dorsal pattern survey showed no statistical difference in dorsal blotch retention among Black Ratsnakes of different areas; however, comparisons of mean values showed that one group of specimens displayed a more uniform and darker pigmentation than the other groups of specimens. West Virginia specimens were intermediate between the two pattern extremes.