02362nas a2200277   4500008004100000245016000041210006900201300001200270490000800282520152300290653000901813653001601822653000901838653001101847653001401858653000901872653001501881653002601896653002401922653002001946653001301966100002001979700001901999700001502018856005102033       2009                        eng d00aStable Isotopes Reveal Seasonal Competition for Resources Between Late Pleistocene Bison (Bison) and Horse (Equus) from Rancho La Brea, Southern California0 aStable Isotopes Reveal Seasonal Competition for Resources Betwee  a153-1600 v2713 a<p>Determining how organisms partition or compete for resources within ecosystems can reveal how communities are assembled. The Late Pleistocene deposits at Rancho La Brea are exceptionally diverse in large mammalian carnivores and herbivores, and afford a unique opportunity to study resource use and partitioning among these megafauna. Resource use was examined in bison and horses by serially sampling the stable carbon and oxygen isotope values found within tooth enamel of individual teeth of seven bison and five horses. Oxygen isotope results for both species reveal a pattern of seasonal enamel growth, while carbon isotope values reveal a more subtle seasonal pattern of dietary preferences. Both species ate a diet dominated by C<sub>3</sub> plants, but bison regularly incorporated C<sub>4</sub> plants into their diets, while horses ate C<sub>4</sub> plants only occasionally. Bison had greater total variation in carbon isotope values than did horses implying migration away from Rancho La Brea. Bison appear to incorporate more C<sub>4</sub> plants into their diets during winter, which corresponds to previous studies suggesting that Rancho La Brea, primarily surrounded by C<sub>3</sub> plants, was used by bison only during late spring. The examination of intra-tooth isotopic variation which reveals intra-seasonal resource use among bison and horse at Rancho La Brea highlights the utility of isotopic techniques for understanding the intricacies of ecology within and between ancient mammals.</p>
10aC-1310aCompetition10aDiet10aEnamel10aMigration10aO-1810aPopulation10aResource partitioning10aSpecies coexistence10aStable isotopes10aUngulata1 aFeranec, R., S.1 aHadley, E., A.1 aPaytan, A.  uhttp://dx.doi.org/10.1016/j.palaeo.2008.10.005