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

尽管生态学家和古生态学家长期以来一直试图了解控制生物多样性的因素，但现代生物危机，如大范围灭绝和外来物种的引入，使得对这种理解的探索日益迫切。现代生态学研究非常适合描述和预测生物入侵期间发生的短期生态相互作用和变化，即外来物种大规模引入一个地区。然而，古生物学研究更适合于记录这些事件的长期影响，以及确定生态系统建立或拆除的规则。以前对生物入侵化石的研究大多来自相对年轻的新生代沉积物（距今6500万年至今）。需要对更古老的生物入侵进行研究，以确定这些年轻生物入侵的结果是否具有整个地质历史中生物入侵的典型特征。保护策略将取决于是否存在一些关于生物入侵的长期影响的简单规则，或者是否任何特定入侵的长期影响是特殊的，不太可能是可预测的。PIs建议记录海洋生态系统如何应对奥陶纪晚期（4.54亿至4.44亿年前）生物入侵，这种入侵影响了从俄亥俄州辛辛那提到田纳西州纳什维尔的浅海群落。具体来说，他们将在这1000万年的时间窗口内确定单个生态群落内部的多样性如何变化（α多样性），生态群落的独特性如何变化（β多样性），以及整个地理区域的多样性如何变化（γ多样性）。由于每一种多样性测量都与特定的生态预测有关，这些预测涉及物种在位性、空缺生态位和物种之间的生态相互作用的重要性，因此我们的研究不仅能够记录多样性分配的变化，还将确定这些变化的生态根源。他们的研究将建立在他们之前在纳什维尔地区的研究基础上，并将使用先进的层序地层框架来重建环境条件，并建立该地区事件的时间序列。PIs期望他们将开发的研究生物入侵的方法可能对研究地质记录的其他部分的生物危机有用。

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.