Morphological evolution and the Cambrian Explosion - a 550 million year view

形态演化与寒武纪大爆发——5.5亿年的视角

• 批准号: NE/W007878/2
• 负责人: Luke Parry
• 金额: $ 69.73万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW007878%2F2
• 关键词: Morphological; evolution; Cambrian; Explosion; 550

The diversity of living animals can be placed into about 30 groups called phyla, a term that refers to the possession of a distinct body plan. All these body plans first appear in the fossil record in a geological blink of an eye, in an event that has been named the Cambrian explosion (about 550-520 million years ago). During this time, animals as different as worms, jellyfish and even our distant relatives can be found as fossils, contrasting with more ancient rocks where most evidence of life is microscopic. The fossils of ancient animals from this time have been difficult to classify, with some scientists previously arguing that the Cambrian represents an 'experimental' phase in animal evolution, with types of animals evolving forms that have never been seen again. The Cambrian Explosion has been considered an entirely unique event in the history of the planet, with evolutionary change occurring faster and with greater magnitude than at any other time. The range of different body forms is referred to as disparity, and some previous studies have proposed that this disparity peaked in the Cambrian and was then educed over time by extinction. Other studies have instead viewed Cambrian fossils as the evolutionary antecedents of living organisms, filling in the gaps that exist between the body plans of groups alive today. However, investigations into these patterns of evolution during the Cambrian have typically focused either on a narrow set of animal groups, most often arthropods (spiders, centipedes and their relatives), or have only considered evidence from Cambrian organisms and those alive today, missing evidence from the intervening 500 million years of Earth History. Since the Cambrian Explosion ended, animals are known to have radically modified their body plans, often when moving to new and sometimes extreme and hostile environments such as the transition from the ocean to life on land or the colonisation of hydrothermal vents. In this project I will use the group of animals called Spiralia to investigate how the diversity of animal forms was shaped since their origin in the Cambrian Explosion to the present. Spiralians are incredibly diverse, encompassing familiar groups like earthworms and snails but also containing a bewildering array of more unusual forms that primarily live in the ocean. Spiralians account for over half of animal body plans and have an excellent fossil record from the earliest phase of the Cambrian explosion onwards. Together these facts highlight this group of organisms as the ideal study system for understanding the evolution of animal disparity. This research project will address the following research questions:Q1. How have patterns of morphospace occupation (disparity) varied through 540 million years of spiralian evolution?Q2. What patterns of evolution along lineages gave rise to these patterns of morphological disparity?I will accomplish this by collecting new data from exceptionally preserved, ancient fossils from the Cambrian and early Ordovician Periods (about 542-480 million years old) which I will combine with data from living species to construct evolutionary diagrams called phylogenies. These are like a family tree and depict the relationships between different types of organisms. Building such a tree of life for spiralians will be a key first step, and will require using information from DNA sequences, fossils and the anatomy of living animals. The resulting evolutionary trees are more than just diagrams as they allow investigation of how evolution has proceeded through time, allowing me to estimate the speed ('rate') of evolutionary changes in the past, and the total amount of change that happened. This will allow me to understand how new morphological variation has been generated over time from the Cambrian to the present day. Finally, it will allow me to understand how the Cambrian Explosion and subsequent events shaped the spectacular biodiversity alive today.

活体动物的多样性可分为大约 30 个类群，称为“门”，该术语指的是拥有独特的身体结构。所有这些身体结构首次出现在化石记录中的时间都在地质学的眨眼之间，发生在一个被称为寒武纪大爆发（大约 550-5.2 亿年前）的事件中。在此期间，各种不同的动物，如蠕虫、水母，甚至我们的远亲，都可以作为化石被发现，这与更古老的岩石形成鲜明对比，在这些岩石中，大多数生命的证据都是微观的。这个时期的古代动物化石很难分类，一些科学家此前认为寒武纪代表了动物进化的“实验”阶段，动物类型进化出了从未见过的形式。寒武纪大爆发被认为是地球历史上一次完全独特的事件，其进化变化比任何其他时期发生得更快、幅度更大。不同身体形态的范围被称为差异，之前的一些研究提出，这种差异在寒武纪达到顶峰，然后随着时间的推移因灭绝而减少。其他研究则将寒武纪化石视为生物体的进化祖先，填补了当今活着的群体的身体计划之间存在的空白。然而，对寒武纪这些进化模式的研究通常要么集中在一小部分动物群体上，最常见的是节肢动物（蜘蛛、蜈蚣及其近亲），要么只考虑来自寒武纪生物和今天活着的生物的证据，缺乏证据距今 5 亿年的地球历史。自寒武纪大爆发结束以来，众所周知，动物已经从根本上改变了它们的身体计划，通常是在迁移到新的、有时甚至是极端和敌对的环境时，例如从海洋过渡到陆地生活或热液喷口的殖民化。在这个项目中，我将使用名为螺旋体的动物群来研究自寒武纪大爆发至今动物形态的多样性是如何形成的。螺旋动物极其多样化，包括蚯蚓和蜗牛等熟悉的群体，但也包含一系列令人眼花缭乱的主要生活在海洋中的更不寻常的形式。螺旋动物占动物体型的一半以上，并且从寒武纪大爆发的最早阶段开始就拥有出色的化石记录。这些事实共同凸显了这组生物体是了解动物差异进化的理想研究系统。该研究项目将解决以下研究问题：Q1。在 5.4 亿年的螺旋演化中，形态空间占据（视差）的模式如何变化？沿谱系的哪些进化模式导致了这些形态差异模式？我将通过从保存完好的寒武纪和奥陶纪早期（约 542-4.8 亿年前）的古代化石中收集新数据来实现这一目标，我将把这些数据与来自活物种的数据来构建称为系统发育的进化图。它们就像一个家谱，描述了不同类型生物之间的关系。为螺旋虫构建这样一棵生命树将是关键的第一步，并且需要使用来自 DNA 序列、化石和活体动物解剖学的信息。由此产生的进化树不仅仅是图表，因为它们允许调查进化如何随时间进行，使我能够估计过去进化变化的速度（“速率”）以及发生的变化总量。这将使我了解从寒武纪到今天，新的形态变化是如何产生的。最后，它将让我了解寒武纪大爆发和随后的事件如何塑造了当今壮观的生物多样性。