CHANGES IN LIMB BONE SIZE OF FLORIDA ODOCOILEUS VIRGINIANUS (MAMMALIA: CERVIDAE) FROM THE EARLY PLEISTOCENE TO HOLOCENE

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.