How do palaeontological data refine our understanding of adaptive radiation and the evolution of modern biodiversity?

剑鱼是公海上长着尖鼻的掠食者;比目鱼是我们在美食上熟悉的、奇怪的不对称的海底生物;鱼是用头上的吸盘搭在鲨鱼身上的真正的食客：很少有鱼类或脊椎动物显示出如此惊人的不同解剖结构或生活方式。尽管它们各不相同，但遗传学研究表明，这些鱼类以及其他几种具有同样奇怪特征的鱼类都是密切相关的，在称为Carangimorpha的生命树中形成了一个树枝。像这样的例子，有着共同祖先的有机体随着时间的推移而出现分支，呈现出不同的体型和生活方式，被称为适应性辐射。以前关于这个主题的研究主要集中在化石记录不佳的生物群体，如变色蜥蜴或慈鲷鱼。然而，化石是确定进化事件时间的唯一直接手段，并产生了通过灭绝从生命之树上修剪下来的解剖学的独特证据;因此，它们对于理解现代生物多样性是如何组装的至关重要。我们的项目旨在利用这一特殊的鱼类群体作为实验室，不仅要了解它们的专业化是如何产生的，还要探索化石如何特别有助于回答这些问题。具体而言，我们将问：（1）导致特殊的carangimorph身体“设计”的起源的步骤是什么？（2）这些变化在地质时代发生了什么？（3）化石告诉我们这些变化发生的速度和方式是什么？ 化石对于回答这些问题至关重要。例如，最近的发现揭示了比目鱼是如何进化到两只眼睛都长在头的一边的。发现这种过渡形式通常是罕见的，但壮观的生活carangimorphs阵列是由完整的化石宝库补充。现代的准备（包括化学处理或类似喷砂的方法）和成像（CT扫描）技术可以用来从周围的岩石中提取化石。我们将揭示特殊化石的细节，这些化石记录了活的carangimorphs适应进化的早期阶段，包括长嘴鱼的剑状吻部和鱼的吸盘。 化石不能为自己说话，我们也不能简单地通过剥开岩层来追踪进化。我们必须发现化石与现存物种的关系。我们将联合收割机古生物学数据与现代鱼类的解剖学和DNA数据相结合，将化石放在一棵树上，与活着的亲戚一起，使我们能够重建导致专门的现代体型的变化序列。包括化石和活物种也很重要，因为化石可以影响活物种之间的估计关系，反之亦然。 为了建立一个卡朗吉莫尔夫进化中主要事件的时间轴，我们需要找出地球历史上家谱中每个分支的分裂时间。石化是一个罕见的事件，因此即使是最古老的化石的一个特定的分支可能是一个相对较晚的到来。因此，我们需要联合收割机将化石数据与一种称为分子钟的间接方法结合起来。如果我们知道基因突变的速度，我们就可以估计出物种在多久以前彼此分离，并产生一个“时间树”：一个具有绝对时间尺度的家谱。有了所有这些组件，我们可以解决有关化石如何影响我们对适应性辐射和生物多样性进化的理解的重要问题。我们的时间树使我们能够应用统计工具来确定解剖特征随时间变化的速率。这可以用来观察在进化史的早期变化是迅速的还是缓慢渐进的，以及海洋和淡水环境之间的进化速度是否不同。重要的是，我们将在有化石和没有化石的情况下进行分析，使我们能够决定仅基于现代数据的研究是否可能产生误导。

Swordfishes, needle-nosed predators of the high seas; flounders, gastronomically familiar and bizarrely asymmetrical bottom dwellers; remoras, literal hangers-on that hitch rides on sharks using a suction cup on their heads: few fishes, or vertebrates, show more strikingly different anatomies or modes of life. Divergent as they are, genetic studies indicate that these fishes, as well as several others with equally curious traits, are all closely related, forming a bough in the tree of life called Carangimorpha. Cases like this, where organisms with shared ancestry branch out over time to assume divergent bodyplans and lifestyles, are known as adaptive radiations. Previous research on this topic has focused on living groups with poor fossil records, like anole lizards or cichlid fishes. However, fossils are the only direct means of timing evolutionary events, and yield unique evidence of anatomies pruned from the tree of life by extinction; as such, they are critical in understanding how modern biodiversity was assembled. Our project seeks to use this exceptional group of fishes as a laboratory to not only understand how their specialisations arose, but also explore the ways in which fossils can be especially useful for answering these questions. Specifically, we will ask: (1) what are the steps leading to the origin of peculiar carangimorph body 'designs'; (2) when in geological time did these changes occur?; and (3) what do fossils tell us about the speed and manner in which these changes took place? Fossils are critical in answering these questions. For instance, recent discoveries revealed how flatfishes evolved to have both eyes on one side of their head. Finding such transitional forms is typically rare, but the spectacular array of living carangimorphs is complemented by a trove of complete fossils. Modern preparation (involving chemical treatment or methods akin to sandblasting) and imaging (CT scanning) techniques can be used to extract fossils from surrounding rock. We will uncover details of exceptional fossils that document the early stages in the evolution of adaptations of living carangimorphs, including the rapier-like snout of billfishes and the suction disc of remoras. Fossils cannot speak for themselves and we cannot simply trace evolution by peeling back rock layers. We must discover the relationships of fossils to living species. We will combine palaeontological data with anatomy and DNA data from modern fishes to place fossils in a tree alongside living relatives, allowing us reconstruct the sequence of changes leading to specialized modern bodyplans. Including both fossils and living species is also important because fossils can influence estimated relationships among living species and vice versa. To build a timeline for major events in carangimorph evolution, we need to find out when in Earth's history each branch in its family tree split off. Fossilization is a rare event, and so even the oldest fossil of a particular branch might be a relatively late arrival. We therefore need to combine our fossil data with an indirect approach known as the molecular clock. If we know the rate at which genetic mutations build up, we can estimate how long ago living species split from each other and produce a 'time tree': a family tree with an absolute time scale. With all of these components in place, we can address important questions about how fossils impact our understanding of adaptive radiation and the evolution of biodiversity. Our time tree allows us to apply statistical tools for determining the rate at which anatomical features changed over time. This can be used to see whether change was rapid early in evolutionary history or whether it was slow and gradual, and whether rates of evolution varied between marine and freshwater environments. Critically, we will conduct our analyses with and without fossils, allowing us to decide whether studies based only on modern data might be misleading.