A thorough understanding of how communities respond to extreme changes, such as biotic invasions, is essential to manage ecosystems today. Here we constructed fossil food webs to identify changes in Late Ordovician (Katian) shallow-marine paleocommunity structure and functioning before and after the Richmondian invasion, a well-documented ancient invasion. Food webs were compared using descriptive metrics and cascading extinction on graphs models. Richness at intermediate trophic levels was underrepresented when using only data from the Paleobiology Database relative to museum collections, resulting in a spurious decrease in modeled paleocommunity stability. Therefore, museum collections and field sampling may provide more reliable sources of data for the reconstruction of trophic organization in comparison to online data repositories. The invasion resulted in several changes in ecosystem dynamics. Despite topological similarities between pre- and postinvasion food webs, species loss occurred corresponding to a minor decrease in functional groups. Invaders occupied all of the preinvasion functional guilds, with the exception of four incumbent guilds that were lost and one new guild, corroborating the notion that invaders replace incumbents and fill preexisting niche space. Overall, models exhibited strong resistance to secondary extinction, although the postinvasion community had a lower threshold of collapse and more variable response to perturbation. We interpret these changes in dynamics as a decrease in stability, despite similarities in overall structure. Changes in food web structure and functioning resulting from the invasion suggest that conservation efforts may need to focus on preserving functional diversity if more diverse ecosystems are not inherently more stable.

中文翻译：

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里士满入侵前后晚奥陶世生态系统动态的比较揭示了入侵物种在底栖海洋古群落中的后果

彻底了解社区如何应对极端变化（例如生物入侵）对于管理当今的生态系统至关重要。在这里，我们构建了化石食物网，以确定晚奥陶世（Katian）浅海古群落结构和功能在里士满入侵前后的变化，这是一次有据可查的古代入侵。使用描述性指标和图模型上的级联灭绝来比较食物网。当仅使用古生物学数据库中相对于博物馆藏品的数据时，中间营养级的丰富度被低估，导致模拟的古社区稳定性虚假下降。因此，与在线数据存储库相比，博物馆藏品和现场采样可以为重建营养组织提供更可靠的数据来源。入侵导致生态系统动态发生了一些变化。尽管入侵前和入侵后食物网之间的拓扑相似性，但物种损失的发生对应于功能组的轻微减少。入侵者占据了入侵前的所有功能性公会，除了丢失的四个现有公会和一个新公会外，这证实了入侵者取代现有公会并填补先前存在的利基空间的概念。总体而言，模型对二次灭绝表现出很强的抵抗力，尽管入侵后社区的崩溃阈值较低，对扰动的反应更多样化。尽管整体结构相似，但我们将这些动态变化解释为稳定性的降低。