Data from: A shift in the long-term mode of foraminiferan size evolution caused by the end-Permian mass extinction

Size is among the most important traits of any organism, yet the factors that control its evolution remain poorly understood. In this study, we investigate controls on the evolution of organismal size using a newly compiled database of nearly 25,000 foraminiferan species and subspecies spanning the past 400 million years. We find a transition in the pattern of foraminiferan size evolution from correlation with atmospheric pO2 during the Paleozoic (400-250 Mya) to long-term stasis during the post-Paleozoic (250 Mya to present). Thus, a dramatic shift in the evolutionary mode coincides with the most severe biotic catastrophe of the Phanerozoic (543 Mya to present). Paleozoic tracking of pO2 was confined to Order Fusulinida, whereas Paleozoic lagenides, miliolids, and textulariids were best described by the stasis model. Stasis continued to best describe miliolids and textulariids during post-Paleozoic time, while random walk was the best supported mode for the other diverse orders. The shift in evolutionary dynamics thus appears to have resulted primarily from the selective elimination of fusulinids at the end of the Permian Period. These findings illustrate the potential for mass extinction to alter macroevolutionary dynamics for hundreds of millions of years.

体型是所有生物体最为核心的性状之一，然而调控其演化的关键机制迄今仍未得到充分阐明。本研究依托全新构建的、涵盖近25000个有孔虫（foraminiferan）物种及亚种、时间跨度达4亿年的数据库，对生物体体型演化的调控机制展开探究。研究发现，有孔虫体型演化的模式存在一次显著转变：古生代（4亿至2.5亿年前）时期，其体型演化与大气氧分压（pO₂）呈显著相关；而在古生代之后（2.5亿年前至今），则转为长期的演化停滞（stasis）。由此可见，演化模式的剧烈转变与显生宙（5.43亿年前至今）发生的最严重生物大灭绝事件高度吻合。古生代时期，仅纺锤虫目（Fusulinida）的体型演化呈现出随大气氧分压变化的追踪模式，而古生代的瓶虫类（lagenides）、粟米虫类（miliolids）及织砂虫类（textulariids）则最符合演化停滞模型。在古生代之后的时段中，粟米虫类与织砂虫类仍最契合演化停滞模型，而其余多样类群的最优演化模式则为随机游走（random walk）。因此，演化动力学的此番转变似乎主要源于二叠纪末期纺锤虫类的选择性灭绝。本研究结果证实，生物大灭绝具备在数亿年尺度上改变宏观演化动力学（macroevolutionary dynamics）的潜在能力。