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

在灭绝时期，连续化石组合的尺寸减小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存在争议。在各种情况下，大小反应早于主要灭绝脉冲，表明它们可能是早期环境破坏的信号。本文提出的项目旨在明确地模拟层序地层格架中的尺寸变化，以从全球范围内分离出局部古环境对这些模式的影响。该方法将侧重于伊朗二叠纪-三叠纪剖面和欧洲各Pliensbachian-Toarcian剖面的软体动物和腕足动物组合的相内和相间比较，从而涵盖灭绝事件之前和期间的广泛的古环境和保存背景。当过滤掉潜在的收集和地层偏差时，这些方法对于定量地解开与气候相关的压力源和养分有效性在驱动模式中的相对贡献是必要的。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附加的大尺寸数据集，考虑适当的相、层序地层和地球化学背景，以了解它们在这些小型化方面的第一次综合元分析中的相对贡献（“小人国效应”）。这些数据集还将用于理清在背景条件下以及在从小型生物危机到与高温事件相关的大规模灭绝等事件期间，物种内尺寸减小、尺寸选择性灭绝/迁移和起源/迁移在驱动尺寸波动方面的相对贡献。

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.