ELT Collaborative Research: Bayesian Paleoclimate Proxies-Transforming the Vertebrate Fossil Record

该项目使用贝叶斯框架将哺乳动物和爬行动物的功能解剖特征与温度、降水和植被覆盖联系起来，使我们能够根据独立的成壤和古植物学证据明确测试这些脊椎动物环境指标，以便重建北美内陆中新世的古气候。我们根据整个动物群而不是单个物种来估计古环境，以便结合外温动物(爬行动物)和吸热动物(哺乳动物)的预测能力。我们的目标是：(1)基于内布拉斯加州州立博物馆的大量化石收藏和选定化石地点的生物分子替代数据，在大平原中部的局部组合和生物群落尺度上建立中新世脊椎动物化石的功能特征数据库；(2)从现代动物群中抽样的特征建立贝叶斯概率气候空间；(3)利用特征气候空间估计中新世古环境，并检验脊椎动物估计值与独立代理之间的一致性；(4)使用基于特征的替代结果来检验关于中大陆植物区系组成的相互竞争的假说，并确定全球气候变化与当地环境在变暖和降温期间的耦合程度。这项研究是对连续的陆生脊椎动物化石记录进行的最全面的分类和解剖学特征分析，我们的方法可以推广到其他替代指标(稳定同位素、生物分子、古植物群)，作为估计古环境的一般方法。我们将通过中新世生成可用于检验大气环流模型和预测未来人为全球气候变化的区域影响的古气候剖面。非技术描述：该项目利用现存哺乳动物和爬行动物的生理和生态与其现代环境之间的关系，利用化石记录重建中新世(530万至2300万年前)北美内陆过去的气候和环境。我们将利用不同生物和化石物种的骨骼解剖所代表的功能特性，如运动方法、饮食特化和体温的生理调节，来重建已知全球气候变化历史中的温度、降水和植物组成。这种方法为古生物学家提供了一种使用化石来理解环境变化的地理复杂性的复杂方法，并提供了中新世实际发生的变化的记录。我们将开发一个新的统计框架来进行这类研究，使我们能够确定不同过去气候的相对概率。例如，环境温度和降雨量与现代蛇的身体大小和尾巴长度相关，并与现代食肉哺乳动物的脚踝骨骼的相对比例相对应。通过在化石组合中测量这些特征，我们可以根据蛇和哺乳动物不同温度和降雨值的相对概率来统计估计过去的气候。我们的方法使我们能够在当地和全球范围内更好地评估生物与气候变化之间的复杂关系，并将提供准确的过去气候值，可用于测试常规环流模型，并改进预测未来气候变化的能力。除了增加我们对这些重要问题的了解外，用于该项目的资金还将为大学本科生和研究生提供地质、解剖学、计算机编程和数学方面的培训。此外，它还将为公众参加科学会议和博物馆展品做出贡献。

This project links functional anatomical traits in mammals and reptiles to temperature, precipitation, and vegetation cover using a Bayesian framework that allows us to explicitly test these vertebrate environmental proxies against independent pedogenic and paleobotanical evidence in order to reconstruct paleoclimates of the North American interior during the Miocene. We build estimates of paleoenvironment from entire faunas rather than individual species in order to combine the predictive strengths of ectotherms (reptiles) and endotherms (mammals). Our objectives are: (1) assemble a database of functional traits from Miocene vertebrate fossils at the local assemblage and biocenosis scale in the central Great Plains based on the extensive fossil collections of the Nebraska State Museum and biomolecular proxy data from select fossil localities; (2) develop Bayesian probabilistic climate spaces from sampled traits in modern faunas; (3) use the trait-climate spaces to estimate Miocene paleoenvironment and test for consilience between vertebrate estimates and independent proxies; (4) use the trait-based proxy results to test competing hypotheses of mid-continental floral composition and to determine the extent of coupling between global climate change and local environments during episodes of warming and cooling. This study is the most taxonomically and anatomically comprehensive analysis of faunal traits ever performed on a continuous terrestrial vertebrate fossil record, and our method can be extended to other proxies (stable isotopes, biomolecules, paleoflora) as a general method for paleoenvironmental estimation. We will generate paleoclimate profiles through the Miocene that can be used to test General Circulation Models and to forecast regional impacts of future anthropogenic global climate change. Non-technical description: This project uses the relationship between the physiology and ecology of living mammals and reptiles to their modern environments to reconstruct the past climates and environments of the interior of North America during the Miocene Epoch (5.3 to 23.0 million years ago) using the fossil record. We will use the functional properties of different living and fossil species that are represented by their skeletal anatomy, such as method of locomotion, dietary specializations, and physiological regulation of body temperature, to reconstruct temperature, precipitation, and floral composition during known histories of global climate change. This approach provides paleontologists with a sophisticated way of understanding the geographic complexity of environmental change using fossils and it provides a record of what changes actually occurred in the Miocene. We will develop a new statistical framework for conducting such research that allows us to determine the relative probabilities of different past climates. For example, environmental temperature and precipitation are correlated to body size and tail length in modern snakes and correspond to the relative proportions of ankle bones in modern carnivorous mammals. By measuring these traits in fossil assemblages, we can statistically estimate past climates based on the relative probabilities of different temperature and precipitation values from both snake and mammals. Our method allows us to better assess the complex relationship between organisms and changing climate at both local and global scales, and will provide precise past climate values that can be used to test General Circulation Models and refine the ability to forecast future climate change. In addition to increasing our understanding about these important issues, the funds spent on this project will provide training in geology, anatomy, computer programing, and mathematics to university undergraduate and graduate students. Additionally, it will contribute to scientific conferences and museum exhibits for the general public.