Literaturdatenbank
Literaturdatenbank |
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Vitek, N. S. , Patterns of morphological variation in the shell of the eastern box turtle (terrapene carolina) (poster). Unpublished paper presented at 2013 Box Turtle Conservation Workshop.
Added by: Admin (06 Jan 2014 18:25:29 UTC) |
| Resource type: Conference Paper BibTeX citation key: anon2013.15748 View all bibliographic details  |
Categories: General Keywords: Emydidae, Habitat - habitat, Morphologie - morphology, Nordamerika - North America, Schildkröten - turtles + tortoises, Terrapene carolina Creators: Vitek Collection: 2013 Box Turtle Conservation Workshop |
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| Abstract |
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An accurate understanding of subspecific structure and variation within the Eastern Box Turtle (Terrapene carolina) can inform conservation efforts, highlighting unique populations or regions that may deserve particular focus. Terrapene carolina was traditionally divided into four extant and one extinct subspecies. The high level of intraspecific variation within the species was assumed to be a reflection of subspecific diversity. However, research based on genetic data has recovered conflicting relationships between some subspecies and no support for others. In addition, researchers studying the largest subspecies have questioned whether supposedly diagnostic features for those groups may simply be features of large-bodied box turtles in general. In order to investigate potential morphological support for the traditionally recognized subspecies, I used geometric morphometrics with two datasets to investigate to what extent size and subspecific identity can explain variation in shell shape. One dataset contained 136 specimens ranging from hatchlings to adults. A second dataset consisted of 200 adult specimens equally distributed across the four extant subspecies recognized in the United States. Specimens in both datasets were compared qualitatively and quantitatively through multiple analyses. Regardless of whether the dataset included or excluded juveniles, size explained a significant component of shape variation. In both datasets, larger turtles were more elongated anteroposteriorly, more bell-shaped dorsoventrally, and had more distinctive marginals in comparison to smaller turtles. The extent to which subspecific identity explained patterns of shape variation was more difficult to assess. Statistical comparisons of mean shape resulted in significant differences between all four nominative subspecies. I found minor differences in a qualitative comparison of average shell shape for each subspecies. In contrast, I found that all of the shell shape of each subspecies was not distinct in morphospace in canonical variates analyses. Additionally, multiple assignments tests based on shell shape could not reliably assign specimens to subspecies. It is possible that those differences between the shell shape of the four nominative subspecies of T. carolina may be significant statistically, but not significant biologically. The results of this study should not be interpreted as an argument against existing subspecific taxonomy of T. carolina. Rather, the results highlight the need for a better understanding of what explains variation, both genetic and phenotypic, within the species and how best to conserve the resulting diversity.
Added by: Admin |