Data from: Effects of mass extinction and recovery dynamics on long-term evolutionary trends: a morphological study of Strophomenida (Brachiopoda) across the Late Ordovician mass extinction

Mass extinctions affect the history of life by decimating existing diversity and ecological structure and creating new evolutionary and ecological pathways. Both the loss of diversity during these events and the rebound in diversity following extinction had a profound effect on Phanerozoic evolutionary trends. Phylogenetic trees can be used to robustly assess the evolutionary implications of extinction and origination. We examine both extinction and origination during the Late Ordovician mass extinction. This mass extinction was the second largest in terms of taxonomic loss but did not appear to radically alter Paleozoic marine assemblages. We focus on the brachiopod order Strophomenida, whose evolutionary relationships have been recently revised, to explore the disconnect between the processes that drive taxonomic loss and those that restructure ecological communities. A possible explanation for this disconnect is if extinction and origination were random with respect to morphology. We define morphospace using principal coordinate analysis (PCO) of character data from 61 Ordovician-Devonian taxa and their 45 ancestral nodes, defined by a most parsimonius reconstruction in Mesquite. A bootstrap of the centroid of PCO values indicates that genera were randomly removed from morphospace by the Late Ordovician mass extinction, and new Silurian genera were clustered within a smaller previously unoccupied region of morphospace. Diversification remained morphologically constrained throughout the Silurian and into the Devonian. This suggests that the recovery from the Late Ordovician mass extinction resulted in a long-term shift in strophomenide evolution. More broadly, recovery intervals may hold clues to understanding the evolutionary impact of mass extinctions.

大灭绝事件（Mass Extinctions）通过摧毁现存的生物多样性与生态系统结构、开辟全新的演化与生态路径，深刻影响生命演化的整体历程。此类事件中发生的生物多样性丧失，以及灭绝后多样性的复苏过程，均对显生宙（Phanerozoic）的演化趋势产生了深远影响。系统发育树（Phylogenetic Trees）可用于可靠评估灭绝与类群起源的演化意义。本研究聚焦奥陶纪晚期（Late Ordovician）大灭绝事件中的灭绝与类群起源过程。该大灭绝事件按分类群丢失量计算为地球历史上第二大灭绝事件，但并未显著改变古生代（Paleozoic）海洋生物群落的组成结构。我们以演化关系近期已得到修订的扭月贝目（Strophomenida，腕足动物目）为研究对象，探讨驱动分类群丢失的过程与重塑生态群落的过程之间存在的脱节现象。针对这一脱节现象的一种可能解释是：灭绝与类群起源过程与生物形态特征无关，即呈随机模式。我们基于61个奥陶纪-泥盆纪类群及其45个祖先节点的性状数据，通过主坐标分析（Principal Coordinate Analysis, PCO）构建形态空间（morphospace）；祖先节点通过Mesquite软件中的最简约重建（most parsimonious reconstruction）确定。对主坐标分析所得质心值的自举法（Bootstrap）检验显示，奥陶纪晚期大灭绝事件随机从形态空间中移除了多个属级类群，而志留纪新生的属级类群则聚集于形态空间中一块此前未被占据的小型区域内。在整个志留纪乃至泥盆纪时期，类群的多样化进程始终受到形态空间的约束。这表明奥陶纪晚期大灭绝事件后的生物复苏，促使扭月贝类的演化发生了长期的方向性转变。从更宏观的尺度而言，生物复苏阶段或许可为理解大灭绝事件的演化影响提供关键思路。