Global and local effects of long-term environmental change : a turtles eye view

海龟、陆龟和龟类（统称为龟类）是一个非常成功的脊椎动物群体，已经生存了超过2.2亿年。它们经历了许多重大的环境扰动，包括晚白垩世和始新世全球温室条件的形成（以及相关的冷却事件），白垩纪末期的大规模灭绝，以及始新世后的全球冷却趋势。他们是如何应对这些过去的环境变化的？我们可以从它们的历史中学到什么，可以用来了解生物群过去和未来对长期环境变化的反应？龟类栖息在全球三大领域（海洋，淡水，陆地）和龟类化石是非常常见的，有一个完善的分类，他们的栖息地偏好是众所周知的。由于所有这些原因，龟类是研究冷血脊椎动物对长期环境变化的生物反应的一个近乎理想的模型系统。这是因为我们可以将不同生境和地区的群体特征作为一个重复的自然实验进行比较，以了解长期变化对全球多样性生态子集的不同影响。此外，龟类在全球范围内受到威胁，研究它们过去对重大环境事件的反应将提供所需的基线信息，以帮助预测它们对预计的未来气候变化的可能反应。我们将建立一个全面的数据库，涵盖中生代和古近纪（2.2亿-2300万年前）的所有龟类事件。我们将使用这些数据来构建有史以来第一次严格估计全球龟的多样性在此期间。我们将应用标准的和新开发的统计方法，从化石记录中的不均匀采样或其他偏差导致的噪声中提取多样性变化的信号。然后，我们将使用这些数据来了解如何龟的多样性模式不同的栖息地和地区。不同地区和栖息地的变化是不同步发生的，还是它们共同作用创造了全球模式？最重要的是，我们将比较所观察到的多样性模式与古气候数据，如平均年温度和降水率，以确定是否有任何显着的积极（进化辐射或减少灭绝）或消极（减少起源或增加灭绝）的变化与全球或区域环境扰动的龟类多样性。所有这些工作将导致对海龟多样性，分布和气候之间关系的最详细的了解。这将极大地推进我们对全球变化的长期生物反应的理解，将及时补充其他群体（主要是哺乳动物）的现有工作，并将为龟类和其他爬行动物当前的生物多样性趋势提供深层次的视角。这些来自化石记录的见解，是唯一能够记录气候变化长期影响的数据集，将与那些研究活物种的人直接相关。我们认为，我们的研究结果将是非常重要的动物学家，保护生物学家，古生物学家，古气候学家和宏观生态学家。

Turtles, tortoises, and terrapins (collectively termed chelonians) are an immensely successful group of vertebrates that have endured for over 220 million years. They have persisted through numerous major environmental perturbations, including the formation of global hothouse conditions in the Late Cretaceous and Eocene (and associated cooling events), the end-Cretaceous mass extinction, and post-Eocene global cooling trends. How have they responded to these past environmental changes? What can we learn from their history that can be applied to understand past and future responses of biota to long-term environmental change? Chelonians inhabit all three major global realms (marine, freshwater, terrestrial) and chelonian fossils are exceptionally common, have a well-established taxonomy, and their habitat preferences are well-understood. For all of these reasons, chelonians are a near-ideal model system for studying the biotic response of cold-blooded vertebrates to long-term environmental change. This is because we can compare groups characteristic of different habitats and regions as a replicated natural experiment to understand the differential effects of long-term change on ecological subsets of global diversity. Moreover, chelonians are globally threatened, and study of their past reactions to major environmental events will provide the baseline information needed to help predict their possible responses to projected future climate change.The proposed project is completely novel. We will build a comprehensive database of all chelonian occurrences in the Mesozoic and Paleogene (220-23 million years ago). We will use these data to construct the first-ever rigorous estimate of global chelonian diversity during this interval. We will apply standard and newly developed statistical methods to extract the signal of diversity change from noise resulting from uneven sampling or other biases in the fossil record. We will then use these data to understand how chelonian diversity patterns differ among habitats and regions. Do changes in different regions and habitats occur out of phase or do they act together to create the global pattern? Most importantly, we will compare the observed diversity patterns with palaeoclimatic data, such as mean annual temperature and precipitation rates, in order to determine if any significant positive (evolutionary radiation or decreased extinction) or negative (decreased origination or increased extinction) changes in chelonian diversity correlate with global or regional environmental perturbations. All of this work will lead to the most detailed understanding of the relationship between chelonian diversity, distribution and climate ever attempted. This will greatly advance our understanding of long-term biotic responses to global change, will be timely in complementing existing work on other groups (primarily mammals), and will provide a deep-time perspective on current biodiversity trends in chelonians and other reptiles. These insights from the fossil record, the only dataset capable of documenting the long-term impacts of climate change, will be of direct relevance to those working on living species. We think that our results will be of major importance to zoologists, conservation biologists, palaeontologists, palaeoclimatologists and macroecologists.