Considerable difficulty has been associated with the taxonomy of the genus Graptemys (Map Turtles and Sawbacks) over the last 50 yr, likely attributable to the relatively recent divergence of lineages and morphological variation within species. One trait that has been inconsistently defined has been the costal scute pattern of Graptemys flavimaculata, with many authors describing various blotch or ring patterns, or both. This study seeks to describe and quantify costal scute pattern via ring presence throughout the range of G. flavimaculata using both contemporary (field-captured) and historical (museum specimen) sources. Comparisons were made for contemporary individuals and historical specimens of both sexes throughout the geographic range. The pattern of all blotches dominated both sources (89.8%), whereas historical specimens had a higher rate of ring presence (15.1%) compared with contemporary individuals (8.6%). For contemporary data, ring presence was lower in headwater reaches (4.1–4.8%), but higher in middle to lower reaches of the river system (8.9–35.5%). Pattern variability might be attributable to environmental selection, incubation temperatures, genetic divergence, or a combination thereof. For historical specimens, geographic patterns observed were incongruent to contemporary data and likely attributable to geographic sampling bias. Considerable temporal and sexual bias was also observed in the specimen record as a result of species protections in the early 1990s and sampling methodology, respectively.

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