Late Pleistocene small mammal faunas from North America are used extensively as proxies for climate changes during the last 20,000 years. The dominant characteristic regarding these Pleistocene biotas is their high species diversity, the existence of non-analog communities (disharmonious faunas), and the individualistic response of species to regional climate change. Because the concept of disharmonious faunas is critical to modeling climate change and the development of biotic communities, this hypothesis must be tested quantitatively---by accelerator mass spectrometry (AMS) C dating of individual fossil species that are now allopatric. The goal is to AMS C date 140 fossils from three stratified caves along an environmental transect: Hall's Cave, Texas; Peccary Cave, Arkansas; and Baker Bluff Cave, Tennessee. In addition, approximately 20 pairs of disharmonious fossil species from single-component sites will be added to the data set. The C dates will 1) evaluate if disharmonious assemblages are natural occurrences, 2) provide chronologies for species migrations and 3) will improve significantly the chronologies for biotic changes during the past 20,000 years. Ultimately, the C dating will provide quantitative data on background levels of faunal change-- data presently unavailable to ecologists.
