MOVING BEYOND THE PRESENT WHEN INFERRING ECOSYSTEMS OF THE PAST: CAUTIONARY LESSONS FROM THE FOSSIL RECORD

Ancient ecosystems, especially terrestrial Cenozoic faunas, are often dependent on the study of extant taxa to make informed interpretations about extinct taxa. While the study of modern and historic specimens can provide important contextual information for inferring ancient ecosystems—many extinct species exhibited behaviors that do not exist today. Conservation paleobiology, the study of fossil ecosystems with the aim of answering modern day ecological questions, can also assist in more informed understandings of the potential ecology of modern taxa—demonstrating the ability of extant taxa to live in different or broader environmental conditions than currently apparent. Here, I synthesize a series of stable isotope and dental microwear texture studies where paleoecological data clearly show a departure from present conditions. Examples include Pleistocene herbivores of North America (bison and horses), megafaunal communities prior to and after the Late Pleistocene extinction event, sabertooth marsupial-like mammals from South America, and extant Australian marsupials that demonstrate a departure from prehistoric ecological conditions. Lessons learned are not universal, but do include: 1) dietary niches are not consistent over space and time; 2) predators and their prey were affected by the megafaunal extinction, with the extinction affecting the ecology of surviving species and their respective niches; 3) similar forms don't always equal similar functions; and, 4) the habitat and ecological requirements of a given taxon may be much broader in the past, than today—a potential consequence of the direct and indirect effects of human presence. As modern day biases can cloud our understanding and interpretation of ancient ecosystems, it is important to acknowledge the benefits and limitations of modern records for clarifying the past.