2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 45-1
Presentation Time: 9:00 AM


GERWITZ, Andrew, Geology, Kent State University, 221 McGilvery Hall, 325 S. Lincoln Street, Kent, OH 44242 and GREEN, Jeremy L., Geology, Kent State University at Tuscarawas, 330 University Dr NE, New Philadelphia, OH 446636

Abundant fossils of Odocoileus virginianus from Florida provide an opportunity to study bone size variation between succeeding populations of a mammal species over the past 2 million years. We test the hypothesis that adult limb bone size in Florida O. virginianus changed in response to environmental shifts during the Pleistocene (PLE) and Holocene (HOL). Mid-diaphyseal circumference (MDC) of 211 adult limb bones (humeri , radii, metacarpals, femora, tibiae, metatarsals) were measured from four sites from Florida, representing two glacial (Inglis 1A-early PLE [ING], Coleman 2A-middle PLE [COL]) and two interglacial sites (Leisey Shell Pit 1A-middle PLE [LSP], Nichol’s Hammock- late HOL [NH]). Mann-Whitney U tests were used to test for significant differences and revealed an overall chronologic decrease in MDC of femora (ING: n=13, mean (x) =6.61 cm; LSP: n=1, x=6.45 cm; COL: n=1, x=6.15 cm; NH: n=4, x=5.59 cm) and radii (ING: n=14, m=5.82 cm; NH: n=5, m=4.82 cm). Significant differences in MDC exist between glacial/interglacial (GL/INTGL) populations in humeri (ING: n=18, m=6.36 cm; NH: n=4, m=5.33 cm; p<0.01), femora (ING vs. NH: p=.04) and radii (ING vs. NH: p<0.01). No significant difference exist between humeri from geographically adjacent GL/INTGL sites (ING vs. LSP: p-value = 0.47). Geographical variation between central Florida (CF) (ING, COL, LSP) and southern Florida (SF) (NH) populations was significant for humeri (C: n=23; S: n=4; p=0.04), femora (C: n=15; S: n=4; p=0.01) and radii (C: n=14; S: n=5; p<0.01). Although LSP and COL yielded sample sizes too low for statistical testing, the observed chronologic decrease in MDC supports directional selection for smaller adult size through the PLE-HOL. Significant differences in MDC between GL/INTGL populations suggest that the shift could be climatically driven, relating to the availability and nutritional content of food resources within different GL/INTGL environments. Even so, the effect of geographical variation in Florida environments may still play a significant role. Continued study of PLE-HOL paleocommunities in Florida can help to discern whether the changes in bone size we report are primarily influenced by chronology, geography, climate, or a combination of all three.