A taxonomic study of the morphological variation and intergradation of Chrysemys picta (Schneider) (Emydidae, Testudines) in West Virginia.

摘要

Two subspecies of Chrysemys picta ( C. p. picta and C. p. marginata) occur in West Virginia. The Allegheny Mountains have historically separated the distribution of C. p. picta and C. p. marginata; however, intergrades occur where ranges overlap. These intergrades display morphological characteristics that are often intermediate to the original subspecies. Morphological variation of C. picta was examined by comparing specimens from possible areas of C. p. picta x C .p. marginata intergradation in West Virginia to geographic areas that are not exposed to subspecies distribution overlap. Characters traditionally used to separate C. p. picta and C. p. marginata were measured on preserved specimens from museum collections. Additional character measurements were also taken for each specimen. Two characters, percent disalignment of the carapacial scutes and scute margin width, were analyzed for morphological variation in populations located across West Virginia. This analysis revealed clinal differences in turtle morphology within different watersheds across the state. Sixteen characters were subject to Canonical Discriminate Analysis, Principle Component Analysis, and Analysis of Variance. Range diagrams, bivariate scatterplots and polygonal diagrams were also constructed from the data. Results showed variation within the species and statistical differences between all groups for characters measuring scute disalignment, scute margin width, and supratemporal stripe width and ratio. Separation of C. p. picta and C. p. marginata was clearly defined, with intergrades intermediate to and overlapping both subspecies; however, intergrades displayed greater similarities to C. p. picta. Because the distribution of C. picta is widespread and complex with extensive morphological variation across its range, areas of intergradation where ranges overlap must be identified and studied for a more complete understanding of the distribution patterns and morphological variation of C. picta in West Virginia.