Data from: Graptoloid diversity and disparity became decoupled during the Ordovician mass extinction

The morphological study of extinct taxa allows for analysis of a diverse set of macroevolutionary hypotheses, including testing for change in the magnitude of morphological divergence, extinction selectivity on form, and the ecological context of radiations. Late Ordovician graptoloids experienced a phylogenetic bottleneck at the Hirnantian mass extinction (~445 Ma), when a major clade of graptoloids was driven to extinction while another clade simultaneously radiated. In this study, we developed a dataset of 49 ecologically-relevant characters for 183 species with which we tested two main hypotheses: (a) could the biased survival of one graptoloid clade over another have resulted from morphological selectivity alone and (b) are the temporal patterns of morphological disparity and innovation during the recovery consistent with an interpretation as an adaptive radiation resulting from ecological release? We find that a general model of morphological selectivity has a low probability of producing the observed pattern of taxonomic selectivity. Selectivity on non-morphological variation, such as geographic range or different physiological tolerances, is more likely the cause. Contrary to predictions from theory on adaptive radiations and ecological speciation, changes in disparity and species richness are uncoupled. We also find that the early recovery is unexpectedly characterized by relatively low morphological disparity and innovation, despite also being an interval of elevated speciation. As it is necessary to invoke factors other than ecology to explain the graptoloid recovery, more complex models may be needed to explain recovery dynamics after mass extinctions.对已灭绝类群的形态学研究，可用于检验一系列多样的宏演化假说，包括验证形态分歧程度的变化、基于形态的灭绝选择性，以及辐射演化的生态背景。奥陶纪晚期的笔石类（graptoloids）在赫南特阶大灭绝事件（~445 Ma）中经历了系统发育瓶颈：当时一个主要的笔石类支系走向灭绝，而另一个支系则同时发生辐射演化。本研究构建了涵盖183个物种、共计49个生态相关性状的数据集，用于检验两大核心假说：（a）笔石类支系间存在偏向性的存活优势，是否仅由形态选择性所导致？（b）复苏期内形态分异度与演化创新的时间模式，是否符合生态释放驱动的适应性辐射这一解释？研究结果显示，仅依靠形态选择性的通用模型，能够重现观测到的分类群选择性模式的概率极低。由非形态性状差异（如地理分布范围或不同生理耐受能力）所介导的选择性，更可能是该模式的成因。与适应性辐射与生态物种形成理论的预测相悖，形态分异度的变化与物种丰富度的变化呈现解耦关系。本研究同时发现，尽管复苏早期的物种形成速率有所升高，但其形态分异度与演化创新程度却相对较低，这一结果与预期不符。由于解释笔石类的复苏过程需要援引生态学以外的其他因素，因此未来或需构建更为复杂的模型，以阐释大灭绝后的复苏动态。