The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


It’s the time of the season for extra chewing: temporal variation in diet and phenotypic plasticity in masticatory elements

JEREMIAH E. SCOTT1, MEGHAN M. EASTMAN1, JOEL HLAVATY1, ANDREW G. MANCINI1, DAVID MURRAY1, JOSEPH P. SCOLLAN, JR.1, KEVIN R. MCABEE1 and MATTHEW J. RAVOSA1,2,3,4.

1Department of Biological Sciences, University of Notre Dame, 2Department of Aerospace and Mechanical Engineering, University of Notre Dame, 3Department of Anthropology, University of Notre Dame, 4Department of Anatomy and Cell Biology, Indiana University School of Medicine–South Bend

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Recent discussions of australopith feeding adaptations have focused on the extent to which the masticatory systems of these species were influenced by seasonal variation in dietary properties. This issue is typically framed in terms of reliance on nonpreferred, mechanically difficult-to-process fallback foods at certain times of the year. Here, we report preliminary results from an ongoing animal-model-based diet-manipulation experiment designed to examine this issue. We obtained 40 weanling white rabbits (five weeks old) that were assigned to three dietary cohorts: pellets only (control); pellets supplemented with hay cubes (“annual”); and pellets supplemented with hay cubes for only part of the 48-week experimental period (“seasonal”). Each subject was imaged longitudinally every two weeks using microCT. From these scans we obtained bone cross-sectional areas in the coronal plane at four sites involved in force resistance during biting and chewing: the mandibular symphysis, condyle, and corpus, and the hard palate. Measurements were size-adjusted using maximum cranial length. At ten weeks into the experiment, annual rabbits had significantly (P<0.05) greater relative cross-sectional areas than control rabbits at the corpus, palate, and condyle. Seasonal rabbits, which received hay for only the first six weeks, differed from control rabbits and were similar to annual rabbits in all variables except corpus cross-sectional area; in the latter variable, annual rabbits were significantly larger. These results confirm previous findings regarding organism-level responses (i.e., phenotypic plasticity) to variation in dietary properties and suggest that such responses are site specific and sensitive to experimental conditions that mimic seasonal variation in diet.

Funding for this research was provided by National Science Foundation grant BCS-1029149/1214767 to MJR.

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