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/W007878/1
• 负责人: Luke Parry
• 金额: $ 81.72万
• 依托单位: University College London
• 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: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW007878%2F1
• 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.

活着的动物的多样性可以放入约30组，称为门，这个术语是指拥有独特的身体计划。所有这些身体计划首先以眼睛的地质眨眼出现在化石记录中，这一事件被称为寒武纪爆炸（大约550-5.5万年前）。在这段时间里，与蠕虫，水母甚至我们遥远的亲戚一样不同的动物可以作为化石，与更古老的岩石形成鲜明对比，大多数生命证据都是微观的。从那时起，古代动物的化石很难分类，一些科学家以前认为寒武纪代表了动物进化中的“实验性”阶段，动物类型的发展形式从未见过。寒武纪爆炸被认为是地球历史上完全独特的事件，其进化变化的发生速度比其他任何时候都更快。不同身体形式的范围称为差异，一些先前的研究提出，这种差异在寒武纪中达到峰值，然后随着时间的流逝而被灭绝教育。相反，其他研究将寒武纪化石视为活生物体的进化前因，填补了当今活着的群体计划之间存在的差距。但是，对寒武纪期间这些进化模式的调查通常集中在狭窄的动物群体上，最常见的是节肢动物（蜘蛛，cent虫及其亲戚），或者仅考虑了当今寒武纪和活着的人的证据，缺少了地球历史上5亿年历史的证据。自从寒武纪爆炸结束以来，众所周知，动物会从根本上改变其身体计划，通常是在转向新的，有时是极端和敌对的环境时，例如从海洋到陆地上的生命或水热通风口的殖民化。在这个项目中，我将使用称为Spiralia的动物组来研究动物形式的多样性，因为它们起源于寒武纪爆炸到现在。 Spiralians非常多样化，涵盖了诸如earth和蜗牛之类的熟悉群体，但还包含一系列令人困惑的更不寻常的形式，主要生活在海洋中。 Spiralians占了一半以上的动物身体计划，并且从寒武纪爆炸的最早阶段就拥有出色的化石记录。这些事实共同凸显了这组生物作为理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：第一季度。形态空间占领的模式如何变化到5.4亿年的螺旋进化？Q2。沿海沿岸的哪些进化模式产生了这些形态差异的模式？我将通过从坎布里群岛和早期奥托维奇时期（约542-4.8亿年历史）的特殊保存的古代化石中收集新数据来实现这一目标（我将与来自活物种的数据结合到结构性进化图中的数据，称为Phylygries。这些就像一棵家谱，描绘了不同类型的生物之间的关系。为螺旋桨建造这样的生命树将是关键的第一步，需要使用DNA序列，化石和活体动物的解剖结构中的信息。所产生的进化树不仅仅是图表，因为它们允许研究进化如何随着时间的流逝进行，使我能够估算过去进化变化的速度（“速率”），以及发生的变化总量。这将使我能够了解如何随着时间的流逝从寒武纪到今天如何产生新的形态变化。最后，这将使我能够理解寒武纪爆炸和随后的事件如何塑造当今壮观的生物多样性。

项目成果

Gilsonicaris from the Lower Devonian Hunsrück slate is a eunicidan annelid and not the oldest crown anostracan crustacean.

• DOI: 10.1098/rsbl.2023.0312
• 发表时间: 2023-08
• 期刊: Biology letters
• 影响因子: 3.3