COLLABORATIVE RESEARCH: Diversity Partitioning during a Marine Biotic Invasion: Middle and Late Ordovician, Cincinnati Arch and Nashville Dome

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ABSTRACTAlthough ecologists and paleoecologists have long sought to understand what controls biotic diversity, modern biological crises such as widespread extinction and the introduction of exotic species have made this search for understanding increasingly urgent. Modern ecological studies are well suited for describing and predicting the short-term ecological interactions and changes that occur during biotic invasions, that is, the large-scale introduction of exotic species to a region. However, paleontological studies are much better suited for documenting the long-term impacts of such episodes as well as identifying the rules by which ecosystems are constructed or dismantled. Most previous studies of fossil biotic invasions have come from relatively young deposits from the Cenozoic Era (from 65 million years old to the present). Study of much older biotic invasions is needed to determine whether the outcome of these younger biotic invasions is typical of biotic invasions throughout geologic history. Conservation strategies will depend on whether a few simple rules for the long-term effects of biotic invasions exist or whether the long-term effects of any given invasion are idiosyncratic and less likely to be predictable.PIs propose to document how a marine ecosystem responded to a Late Ordovician (454 to 444 million years ago) biotic invasion that affected shallow marine communities in the region stretching from Cincinnati, Ohio to Nashville, Tennessee. Specifically, they will determine for this 10 million-year window of time how diversity changed within individual ecological communities (alpha diversity), how the distinctiveness of ecological communities changed (beta diversity), and how the diversity changed over this entire geographic region (gamma diversity). Because each of these measures of diversity is linked to specific ecological predictions regarding the importance of incumbency of species, vacant ecological niches, and ecological interactions between species, our study will be able not only to document changes in diversity partitioning, but will identify the ecological roots of those changes. Their research will build on their previous studies in the Nashville region and will use advanced sequence-stratigraphic frameworks to reconstruct environmental conditions and to establish the temporal sequence of events within the region. PIs expect that the methods they will develop for studying biotic invasions may be useful for studying biotic crises in other parts of the geological record.