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

该项目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，使用贝叶斯框架，使我们能够明确测试这些脊椎动物环境代理对独立的成壤和古植物学证据，以重建中新世期间北美内陆的古气候。我们从整个动物群而不是单个物种建立古环境的估计，以便将外温动物（爬行动物）和内温动物（哺乳动物）的预测优势联合收割机。我们的目标是：（1）基于内布拉斯加州立博物馆的大量化石收藏和来自选定化石地点的生物分子代用数据，在大平原中部的当地组合和生物群落规模上，从中新世脊椎动物化石中收集功能特征数据库;（2）从现代动物群的采样特征中开发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用指标的一致性;（4）使用基于特质的代理结果来检验竞争性假设，大陆植物区系组成，并确定全球气候变化和当地环境之间的耦合程度在变暖和变冷的事件。这项研究是最分类学和解剖学上的动物区系特征进行了连续的陆生脊椎动物化石记录的全面分析，我们的方法可以扩展到其他代理（稳定同位素，生物分子，古植物区系）作为古环境估计的一般方法。我们将生成中新世的古气候剖面，可用于测试大气环流模型，并预测未来人为全球气候变化的区域影响。 非技术性说明：该项目利用现存哺乳动物和爬行动物的生理和生态与现代环境之间的关系，利用化石记录重建中新世时期（530万年至2300万年前）北美内陆过去的气候和环境。我们将使用不同的活的和化石物种的功能特性，由他们的骨骼解剖，如运动的方法，饮食专业化，和体温的生理调节，重建温度，降水和花卉组成在已知的全球气候变化的历史。这种方法为古生物学家提供了一种复杂的方法，可以利用化石来理解环境变化的地理复杂性，并记录了中新世实际发生的变化。我们将开发一个新的统计框架进行这样的研究，使我们能够确定不同的过去气候的相对概率。例如，环境温度和降水量与现代蛇类的体型和尾巴长度相关，与现代食肉哺乳动物的踝关节骨的相对比例相对应。通过测量化石组合中的这些特征，我们可以根据蛇和哺乳动物不同温度和降水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更好地评估生物体与局部和全球尺度气候变化之间的复杂关系，并将提供精确的过去气候值，可用于测试大气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理解外，花在这个项目上的资金还将为大学本科生和研究生提供地质学、解剖学、计算机编程和数学方面的培训。此外，它还将为科学会议和博物馆展览作出贡献。

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.