Exceptional record of mid-Pleistocene vertebrates helps differentiate climatic from anthropogenic ecosystem perturbations

doi:10.1073/pnas.0402592101

Exceptional record of mid-Pleistocene vertebrates helps differentiate climatic from anthropogenic ecosystem perturbations

^*Museum of Paleontology, Museum of Vertebrate Zoology, and Department of Integrative Biology, University of California, Berkeley, CA 94720; ^‡Department of Geological Sciences, University of Texas, Austin, TX 78712; ^§Department of Biological Sciences, University of North Carolina, Wilmington, NC 28403; ^¶Department of Biology, Andrews University, Berrien Springs, MI 49104; ^∥Department of Geology and Quaternary Sciences Program, Northern Arizona University, Flagstaff, AZ 86011; ^**Denver Museum of Nature and Science, 2001 Colorado Boulevard, Denver, CO 80205; and ^††Division of Geological Sciences, San Bernardino County Museum, Redlands, CA 92374

Communicated by Estella B. Leopold, University of Washington, Seattle, WA, April 12, 2004 (received for review December 16, 2003)

Abstract

Mid-Pleistocene vertebrates in North America are scarce but important for recognizing the ecological effects of climatic change in the absence of humans. We report on a uniquely rich mid-Pleistocene vertebrate sequence from Porcupine Cave, Colorado, which records at least 127 species and the earliest appearances of 30 mammals and birds. By analyzing >20,000 mammal fossils in relation to modern species and independent climatic proxies, we determined how mammal communities reacted to presumed glacial–interglacial transitions between 1,000,000 and 600,000 years ago. We conclude that climatic warming primarily affected mammals of lower trophic and size categories, in contrast to documented human impacts on higher trophic and size categories historically. Despite changes in species composition and minor changes in small-mammal species richness evident at times of climatic change, overall structural stability of mammal communities persisted >600,000 years before human impacts.