Echinoderms make up a substantial component of Ordovician marine invertebrates, yet their speciation and dispersal history as inferred within a rigorous phylogenetic and statistical framework is lacking. We use biogeographic stochastic mapping (BSM; implemented in the R package BioGeoBEARS) to infer ancestral area relationships and the number and type of dispersal events through the Ordovician for diploporan blastozoans and related species. The BSM analysis was divided into three time slices to analyze how dispersal paths changed before and during the great Ordovician biodiversification event (GOBE) and within the Late Ordovician mass extinction intervals. The best-fit biogeographic model incorporated jump dispersal, indicating this was an important speciation strategy. Reconstructed areas within the phylogeny indicate the first diploporan blastozoans likely originated within Baltica or Gondwana. Dispersal, jump dispersal, and sympatry dominated the BSM inference through the Ordovician, while dispersal paths varied in time. Long-distance dispersal events in the Early Ordovician indicate distance was not a significant predictor of dispersal, whereas increased dispersal events between Baltica and Laurentia are apparent during the GOBE, indicating these areas were important to blastozoan speciation. During the Late Ordovician, there is an increase in dispersal events among all paleocontinents. The drivers of dispersal are attributed to oceanic and epicontinental currents. Speciation events plotted against geochemical data indicate that blastozoans may not have responded to climate cooling events and other geochemical perturbations, but additional data will continue to shed light on the drivers of early Paleozoic blastozoan speciation and dispersal patterns.

中文翻译：

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估计奥陶纪生物多样性大事件中双孔囊胚动物（棘皮动物）的扩散和进化动力学

棘皮动物是奥陶纪海洋无脊椎动物的重要组成部分，但缺乏在严格的系统发育和统计框架内推断的它们的物种形成和传播历史。我们使用生物地理随机映射（BSM；在 R 包 BioGeoBEARS 中实现）来推断双孔胚泡动物和相关物种的祖先区域关系以及通过奥陶纪扩散事件的数量和类型。BSM 分析分为三个时间片，以分析在奥陶纪生物多样性大事件 (GOBE) 之前和期间以及晚奥陶世大规模灭绝间隔内扩散路径如何变化。最适合的生物地理模型结合了跳跃扩散，表明这是一种重要的物种形成策略。系统发育中的重建区域表明第一批双孔囊胚可能起源于波罗的海或冈瓦纳。分散、跳跃分散和同源性在奥陶纪的 BSM 推理中占主导地位，而分散路径随时间变化。早奥陶世的长距离扩散事件表明距离不是扩散的重要预测因素，而波罗的海和劳伦蒂亚之间的扩散事件在 GOBE 期间明显增加，表明这些区域对囊胚物种形成很重要。在晚奥陶世，所有古大陆的扩散事件都有所增加。扩散的驱动因素归因于洋流和陆上洋流。