Dinosaur/plant interactions: testing co-evolutionary patterns over geological timescales

当两个（或更多）物种相互作用时，一个物种的进化影响另一个物种的进化，反之亦然（例如，花和昆虫传粉者），就会发生共同进化。对活生物体的实验研究表明，共同进化在促进进化辐射方面起着重要作用，但尚不清楚这在生命史上的重要程度。在地质时间尺度上，人们提出了许多看似合理的例子（例如，哺乳动物在捕食者和猎物之间的大脑大小和奔跑能力方面的“军备竞赛”），但这些例子很少得到定量测试，而且它们仍然存在争议。在这里，我们建议对白垩纪时期（1.45 -65亿年前）食草恐龙和植物之间共同进化相互作用的许多假设进行测试。这些生物提供了一个模型系统，可以被视为评估共同进化在延长时间尺度上的重要性的测试案例。我们将在对科学文献进行详尽调查的基础上，建立一个关于白垩纪恐龙和植物全球分布的综合数据库。我们将在这些数据中添加当时的环境条件信息（例如气候），所有这些信息将被纳入地理信息系统（GIS）。地理信息系统是一种以计算机为基础的工具，使人们能够可视化和分析空间信息。这将使我们能够对恐龙和植物在时间和空间上的分布进行详细的比较（例如，开花植物科与特定恐龙属；重达1000公斤的大型恐龙与树叶类型）。我们还将把这两个群体的化石记录与其他变量（如气候、纬度、岩石类型）进行比较。地理信息系统将允许在前所未有的详细程度上检验这些联系，它还将提供统计工具来定量分析这些模式。该项目代表了GIS技术在扩展地质时间尺度上测试进化问题的新应用。利用这种方法，我们将在以下几大类中检验各种关于恐龙-植物共同进化的假设：(1)提出恐龙颌部机制进化与白垩纪植物类群之间的相关性；(2)环境对恐龙和植物类群时空分布的控制作用；(3)恐龙和植物身体类型之间的共同进化和生态关联（例如，突出恐龙体重和植物形态等变量之间的比较）；(4)特定植物和恐龙物种之间紧密的共同进化相互作用。恐龙与植物种群或体型之间存在特定的重复关联，这与共同进化是一致的；相反，缺乏这种联系将会使共同进化假说不成立。然而，负面结果可能以前所未有的准确性提供恐龙/植物环境偏好的明确信号。提议的测试还解决了一个更普遍的问题，即共同进化的假设是否真的得到化石证据的支持。因此，这一分析将提供第一个经验检验，证明在白垩纪时期，食草恐龙和植物可以说是共同进化的。

Co-evolution happens when two (or more) species interact with each other so that the evolution of one influences the evolution of the other, and vice versa (e.g., flowers and insect pollinators). Experimental studies on living organisms show that co-evolution plays a major role in promoting evolutionary radiations, but it is unclear to what extent this has been important in the history of life. On geological timescales, many plausible examples have been proposed (e.g., in mammals 'arms races' in brain size and running ability between predators and prey), but few of these have been tested quantitatively, and they remain controversial. Here, we propose to provide tests of the numerous hypotheses that have posited co-evolutionary interactions between herbivorous dinosaurs and plants during the Cretaceous Period (145-65 million years ago). These organisms provide a model system that can be viewed as a test case for assessing the importance of co-evolution over extended timescales. We will construct a comprehensive database on the global distributions of Cretaceous dinosaurs and plants, based on an exhaustive survey of the scientific literature. To these data we will add information on environmental conditions at the time (e.g., climate), and all of this will be incorporated into a Geographical Information System (GIS). The GIS is a computer-based tool that allows one to visualise and analyse spatial information. This will enable us to make detailed comparisons of the distributions in time and space of dinosaurs and plants (e.g., flowering plant families vs. specific dinosaur genera; large dinosaurs > 1, 000 kg vs. types of foliage). We will also compare the fossil records of the two groups with other variables (e.g., climate, latitude, rock type). GIS will allow these associations to be tested at an unprecedented level of detail, and it will also provide statistical tools for analysing such patterns quantitatively. This project represents a novel application of GIS techniques to testing of evolutionary questions over extended geological timescales. Using this approach we will test a variety of hypotheses of dinosaur-plant co-evolution in the following broad categories: (1) proposed correlations between the evolution of dinosaur jaw mechanisms and Cretaceous plant groups; (2) environmental controls on the distribution of dinosaur and plant taxonomic groups in time and space; (3) co-evolutionary and ecological associations between dinosaur and plant body types (highlighting, for example, comparisons between variables such as dinosaur body mass and plant morphology); (4) tight co-evolutionary interactions between specific plant and dinosaur species. The presence of specific repeated associations between dinosaur and plant groups or body types would be consistent with co-evolution; conversely, the lack of such associations would falsify co-evolutionary hypotheses. Negative results could, however, provide a clear signal of dinosaur/plant environmental preferences at a hitherto unprecedented level of accuracy. The proposed tests also address the more general issue of whether hypotheses of co-evolution are actually supported by the fossil evidence. This analysis will therefore provide the first empirical test of the extent to which herbivorous dinosaurs and plants can be said to have co-evolved during the Cretaceous Period.