Data from: The role of regional survivor incumbency in the evolutionary recovery of calcareous nannoplankton from the Cretaceous/Paleogene (K/Pg) mass extinction

The earliest Paleocene record of calcareous nannoplankton presents a unique opportunity to understand the evolutionary recovery of life from mass extinction. Nannoplankton were devastated at the Cretaceous/Paleogene boundary and their subsequent recovery can be studied in great detail because of their abundance in sediments, continuous stratigraphic occurrence and near global distribution. Here we determine when and where new species of nannoplankton originated and how they dispersed following the Cretaceous/Paleogene mass extinction. Initially, we focus our efforts on North Pacific and South Atlantic deep-sea sites with orbital age control to compare the precise timing and dynamics of the recovery between the locations. We then broaden our investigation to six sites from different basins and a variety of environments to study global patterns of the initial recovery. Our results show that many taxa in key Paleogene lineages originated in the North Pacific Ocean and that assemblages comprised primarily of new Paleogene taxa were not observed at other sites for several hundred thousand years. Survivors that were adapted to eutrophic post-extinction conditions rapidly expanded in Southern Hemisphere sites where they dominated assemblages for most of the initial recovery. We therefore hypothesize that groups of survivors formed regionally incumbent assemblages in the Southern Hemisphere that limited diversification and dispersal of new Paleogene taxa. The end of survivor dominance correlates to the recovery of the biologic pump and subsequent decrease in surface ocean nutrient concentration 300-400 Kyr after the boundary. Only after survivors were removed did new Paleogene nannoplankton assemblages become abundant globally. Our results indicate that competition from regionally incumbent survivors was as an important control on the K/Pg recovery of nannoplankton.古新世（Paleocene）钙质超微浮游生物（calcareous nannoplankton）的最早化石记录，为探究生命在大灭绝事件后的演化复苏提供了独一无二的研究契机。超微浮游生物在白垩纪-古近纪（Cretaceous/Paleogene，简称K/Pg）界线处遭受重创，由于其在沉积物中丰度极高、地层产出连续且近乎全球分布，可对其后续的复苏过程开展精细研究。本研究旨在厘清白垩纪-古近纪大灭绝后，超微浮游生物新物种的起源时间、起源地点以及扩散路径。研究初期，我们聚焦于拥有轨道调谐年代控制（orbital age control）的北太平洋与南大西洋深海钻孔位点，以对比两地复苏的精确时序与动力学特征。随后我们将研究范围扩展至不同盆地与多种环境下的6个钻孔位点，以探讨初始复苏的全球分布模式。研究结果显示，关键古近纪支系中的诸多分类群起源于北太平洋海域，且在其后数十万年的时间里，其他研究位点均未出现以古近纪新物种为主的生物组合。适应灭绝后富营养化环境的残存类群在南半球钻孔位点快速扩张，并在初始复苏的绝大多数时段中占据群落主导地位。据此我们提出假说：残存类群在南半球形成了区域性优势驻留群落，这限制了古近纪新类群的多样化进程与扩散范围。残存类群主导地位的终结，与界线后30至40万年（Kyr）间生物泵（biologic pump）的复苏以及表层海水营养盐浓度的下降相吻合。直至残存类群的主导地位被取代后，古近纪超微浮游生物的新组合才在全球范围内变得丰富多样。本研究结果表明，来自区域性优势残存类群的种间竞争，是控制超微浮游生物K/Pg大灭绝后复苏进程的重要调控因素。