Literaturdatenbank
Literaturdatenbank |
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Marcil-Ferland, D. (2009). Geometric morphometrics offer insight on the intersexual differences in allometric coefficients of bite force in the northern map turtle (graptemys geographica). Unpublished thesis , University of Ottawa.
Added by: Sarina Wunderlich (25 Jan 2011 10:32:05 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: MarcilFerland2009 View all bibliographic details  |
Categories: General Keywords: Chrysemys, Chrysemys picta, Emydidae, Ernährung = nutrition, Graptemys, Graptemys geographica, Morphologie = morphology, Physiologie = physiology, Schildkröten = turtles + tortoises Creators: Marcil-Ferland Publisher: University of Ottawa |
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| Abstract |
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Graptemys geographica Chrysemys picta Research has shown that northern map turtles exhibit significant female biased trophic size dimorphism. This dimorphism results in females having a greater bite force than males. However, recent research has demonstrated that males achieve higher allometric coefficients of bite force than females. This intersexual difference in bite performance relative to size could possibly be explained by a divergence of skull morphology. We tested map turtles for intersexual differences in skull morphology by performing geometric morphometric analyses on landmarked skull radiographs. We used painted turtles, a species with no documented trophic size dimorphism, as a control. A principal component analysis (PCA) of landmark data revealed that important intersexual separation occurs along the first principal component axis in map turtles but not in painted turtles. Further analysis of PCA results indicated that male map turtles differed from females by their elongated jaw abductor muscle chamber and smaller temporal fossa. Results from a discriminant function analysis on these same data indicate that intersexual differences in skull shape are significant for map turtles but not for painted turtles. Our results indicate that there exist intersexual differences in skull morphology in the northern map turtle. These differences occur in an area of the skull – the jaw abductor muscle chamber – which has previously been documented to affect bite performance. Because we didn’t observe similar differences in our omnivorous nondimorphic control species, the observed divergence in skull morphology could possibly be an adaptation by male map turtles to sustain themselves on a molluscivorous diet despite constraints on the size of their heads.
Added by: Sarina Wunderlich |