Data from: Environmental and biological controls on the diversity and ecology of Late Cretaceous through early Paleogene marine ecosystems in the U.S. Gulf Coastal Plain

The late Mesozoic through early Cenozoic is an interval of significant biologic turnover and ecologic reorganization within marine assemblages, but the timing and causes of these changes remain poorly understood. Here, we quantify the pattern and timing of changes in the diversity (richness and evenness) and ecology of local (i.e., sample level) mollusk-dominated assemblages during this critical interval using field-collected and published datasets from the US Gulf Coastal Plain. We test whether the biologic and ecologic changes observed primarily at the global level during this time are also expressed at the local level, and whether the end Cretaceous (K/Pg) mass extinction and recovery moderated these trends. To explore whether environment had any effect on these patterns, we examine data from shallow subtidal and offshore settings. Assemblages from both settings recovered to pre-extinction diversity levels rapidly, in less than 7 million years. Following initial recovery, diversity remained relatively unchanged in both settings. The trajectory of ecological restructuring was distinct for each setting in the wake of the K/Pg extinction. In offshore assemblages, the abundance and number of predatory carnivorous taxa dramatically increased, and surficial sessile suspension feeders were replaced by more active suspension feeders. In contrast, shallow subtidal assemblages did not experience ecological reorganization following the K/Pg extinction. The distinct ecological patterns displayed in each environment follow onshore-offshore patterns of innovation, whereby evolutionary novelties first appear in onshore settings relative to offshore habitats. Increased predation pressure may explain the significant ecological restructuring of offshore assemblages, whereby the explosive radiation of predators drove changes in their prey. Habitat-specific ecological restructuring, and its occurrence solely during the recovery interval, implies that disturbance and incumbency were also key in mediating these ecological changes.

晚中生代至早新生代是海洋生物组合发生重大生物更替与生态重构的关键时期，但此类转变的发生时序与驱动机制至今仍未得到充分阐明。本研究依托美国墨西哥湾沿岸平原的野外采集数据与已发表数据集，量化了该关键时期内局域（即样品尺度）软体动物主导的生物组合（mollusk-dominated assemblages）的多样性（丰富度与均匀度）及生态特征的变化模式与发生时序。我们旨在检验：此时期全球尺度下观测到的生物与生态转变是否同样体现在局域尺度，以及白垩纪末期（K/Pg）集群灭绝与后续复苏是否对上述变化趋势产生了调节作用。为探究环境是否对上述格局产生影响，我们分析了浅潮下带与远海生境的相关数据。两类生境的生物组合均在不足700万年的时间内快速恢复至灭绝前的多样性水平。初始复苏完成后，两类生境的多样性均保持相对稳定。K/Pg灭绝事件后，两类生境的生态重构轨迹存在显著差异。在远海生物组合中，肉食性捕食类群的丰度与类群数量显著增加，表层固着悬浮食性生物被活动性更强的悬浮食性生物所取代。与之相反，浅潮下带生物组合在K/Pg灭绝事件后未发生生态重构。两类生境所呈现的差异化生态格局符合岸-海梯度的演化创新模式：相较于远海生境，演化新特征最先出现于近岸生境。捕食压力的增强或可解释远海生物组合的显著生态重构——捕食类群的爆发式辐射演化驱动了猎食对象的类群更替。生境特异性的生态重构仅发生于复苏期内，这表明扰动与在位优势同样是介导此类生态转变的关键因素。