Global and local effects of long-term environmental change: a turtle's eye view

海龟、陆龟和陆龟（统称为龟类动物）是一种非常成功的脊椎动物，它们已经生存了2.2亿年以上。它们经历了许多主要的环境扰动，包括白垩纪晚期和始新世的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，可以应用于理解生物群对长期环境变化的过去和未来的反应？龟类动物生活在全球三大领域（海洋、淡水、陆地），龟类化石非常普遍，有一个完善的分类体系，它们的栖息地偏好也很好理解。由于所有这些原因，龟类动物是研究冷血脊椎动物对长期环境变化的生物反应的近乎理想的模型系统。这是因为我们可以比较不同栖息地和地区的种群特征，作为一个重复的自然实验，以了解长期变化对全球多样性生态子集的不同影响。此外，龟类动物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，帮助预测它们对预测的未来气候变化可能做出的反应。这个提议的项目完全是新奇的。我们将建立一个完整的中生代和古近纪（2.2 - 2300万年前）所有龟栖产状的数据库。我们将利用这些数据构建这段时间内全球龟类多样性的首次严格估计。我们将采用标准的和新开发的统计方法，从化石记录中由于采样不均匀或其他偏差而产生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不同栖息地和地区的龟多样性模式是如何不同的。不同地区和栖息地的变化是不同步的，还是共同作用形成了全球格局？最重要的是，我们将把观察到的多样性模式与古气候数据（如年平均温度和降水率）进行比较，以确定龟类多样性的任何显著的正（进化辐射或减少灭绝）或负（减少起源或增加灭绝）变化是否与全球或区域环境扰动相关。所有这些工作将导致对龟类多样性、分布和气候之间关系的最详细的了解。这将极大地促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，并将为当前龟类和其他爬行动物的生物多样性趋势提供一个深入的视角。化石记录是唯一能够记录气候变化长期影响的数据集，这些来自化石记录的见解将与那些研究现存物种的人直接相关。我们认为我们的结果将对动物学家、保护生物学家、古生物学家、古气候学家和宏观生态学家具有重要意义。

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.