Size reductions during hyperthermal events: early warnings of environmental deterioration or signs of extinction? (EarlyWarn)

在灭绝时期，连续化石组合的大小减少是在各种时间和空间尺度上可见的主要特征。然而，潜在的环境驱动因素和机制仍有争议。在不同的情况下，大小的反应早于主要的灭绝脉冲，这表明它们可能是早期环境破坏的信号。这里提出的项目的目的是明确建模的规模变化的层序地层框架解开这些模式从全球的本地古环境的影响。这种方法将侧重于内相和相之间的比较，软体动物和腕足动物组合的二叠纪-三叠纪在伊朗和各种欧洲Pliensbachian-Toarcian部分，因此涵盖了广泛的古环境和灭绝事件之前和之间的环境背景。这些方法是必要的，以定量解开气候相关的压力和养分供应的驱动模式时，过滤出潜在的收集和地层偏见的相对贡献。该项目的最后一部分将比较我们新收集的高分辨率数据与新添加的大尺寸数据集，考虑适当的相，层序地层和地球化学背景，以了解它们在第一次综合荟萃分析中对小型化（“小人国效应”）的相对贡献。这些数据集还将用于解开物种内大小减少，大小选择性灭绝/移民和起源/移民在背景条件下以及在从轻微生物危机到与超高温事件相关的大规模灭绝的事件中驱动大小波动的相对贡献。

Size reductions in successive fossil assemblages during times of extinction are major features visible across a variety of temporal and spatial scales. The underlying environmental drivers and mechanisms are however still debated. In various cases, size responses predate the main extinction pulse suggesting that they might signal early environmental disruptions. The project proposed here aims to explicitly model size changes in a sequence stratigraphic framework to disentangle the local paleoenvironmental influences on these patterns from global ones. This approach will focus on within-facies and between-facies comparisons of mollusk and brachiopod assemblages of Permian-Triassic sections in Iran and various European Pliensbachian-Toarcian sections, hence covering a wide range of paleoenvironmental and preservational contexts before and across extinction events. These approaches are necessary to quantitatively disentangle the relative contribution of climate-related stressors and nutrient availability in driving patterns when filtering out potential collection and stratigraphy biases. The final part of the project will compare our newly collected high-resolution data with newly appended large size datasets considering appropriate facies, sequence stratigraphic and geochemical context to understand their relative contribution in the first comprehensive meta-analysis on these aspects of miniaturization (“Lilliput effect”). These datasets will also be used to disentangle the relative contribution of within-species size reductions, size-selective extinction/immigration and origination/immigration in driving size fluctuations during background conditions as well as during events ranging from minor biological crises to mass extinctions associated with hyperthermal events.