The dawn of the Phanerozoic: non-bilaterian evolution and the nature of the Cambrian Explosion

显生宙的黎明：非两侧对称演化和寒武纪大爆发的本质

基本信息

批准号：
NE/W00786X/1
负责人：
Frances Dunn
金额：
$ 77.17万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2022
资助国家：
英国
起止时间：
2022 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FW00786X%2F1
关键词：
dawn Phanerozoic non bilaterian evolution

项目摘要

The rise of the animals was a profound transition in the History of Life; for the first-time organisms were able to engineer the environment around them, altering geochemical cycles, building complex ecosystems and diversifying into myriad forms. However, the rise of the animals is also one of the most controversial episodes in Earth History. Recognisable animals appear in the fossil record in great number during the Cambrian Period - the so-called 'Cambrian Explosion', but Darwin's theory of evolution by natural selection demands a longer evolutionary history of animals, stretching deep into the Precambrian (between 4,000-539 million years ago). Indeed, data from DNA also suggests a deep Precambrian root for the animals and this mismatch gets larger the closer we go to the root of the animal tree, for example, the mismatch between genetic estimates for the origin of sponges and the accepted fossil record of that group is on the order of hundreds of millions of years. I intend to better constrain the origin and diversification of animals by studying these particularly ancient lineages, like sponges. Most studies looking at this question tend to focus on bilaterian animals - animals with left-right symmetry - but the older non-bilaterian lineages which, by virtue of their greater age are likely to have a more protracted fossil record have been understudied. This proposal seeks to redress the balance by achieving three distinct research objectives: 1) The Ediacaran (latest Precambrian) macrobiota, which appear in the fossil record around 570 million years ago are a group of organisms with long-extinct bodyplans but that increasing evidence is showing that at least some of which represent the remains of ancient non-bilaterian animals. Because of their strange anatomies they are not often included in studies on the early evolutionary history of the animals and so remain something of an elephant-in-the-room. I intend to study the youngest of the Ediacaran macrobiota - the erniettomorphs - which are a group of organisms made up of serially-repeated tubes - and are amongst the most enigmatic, with no consensus about what they were or, indeed, were not. I will study their affinities by analysing how these organisms grew and developed, using a methodology I have previously designed. I will also establish the evolutionary trajectory of the erniettomorphs as relating to other animals (if appropriate) through a combination of field work and studying museum collections in order to work out when they stopped innovating (varying their bodyplans) and when they went extinct.2) Sponges are often considered to be the most ancient animal lineage, but the oldest widely accepted sponge body fossils are only Cambrian in age. There are, however, a number of putative Ediacaran sponges which may go some way to extend the fossil record more in line with molecular expectations. I will re-examine the morphology of these fossils using large photo datasets and new and unpublished field specimens to assess whether they likely represent ancient sponges. I will also use computational fluid dynamics - a technique which models fluid flow around organisms - to assess whether the anatomy of these fossils allowed them to function as living sponges do. If any of these fossils are likely to be ancient sponges, I will include them in a morphological phylogenetic analysis to understand the sponge tree of life, alongside other, younger sponge fossils. I will then integrate this anatomical and fossil-age data with DNA data to establish the most rigorous estimate of the age of the sponges. 3) I will integrate the above data with previously collected data on other members of the Ediacaran macrobiota and cnidarians (the group containing anemones, corals and jellyfish) to ask whether the rate of anatomical change in the non-bilaterian animals was indeed faster in the late Precambrian (Ediacaran) or conforms to the expectations of the Cambrian Explosion hypothesis.

动物的崛起是生命史上的一次深刻转变。生物体第一次能够改造周围的环境，改变地球化学循环，建立复杂的生态系统并多样化为无数的形式。然而，动物的崛起也是地球历史上最具争议的事件之一。在寒武纪时期，化石记录中大量出现了可识别的动物，即所谓的“寒武纪大爆发”，但达尔文的自然选择进化论要求动物有更长的进化历史，一直延伸到前寒武纪（4,000-539 年）万年前）。事实上，来自 DNA 的数据还表明，动物有很深的前寒武纪根源，而且我们越接近动物树的根源，这种不匹配就会越大，例如，海绵起源的遗传估计与公认的海绵化石记录之间的不匹配。该群体的寿命约为数亿年。我打算通过研究海绵等特别古老的谱系来更好地限制动物的起源和多样化。大多数关注这个问题的研究都倾向于关注两侧对称动物（左右对称的动物），但较古老的非两侧对称动物谱系由于年龄较大，可能拥有更长久的化石记录，但尚未得到充分研究。该提案旨在通过实现三个不同的研究目标来纠正这种平衡：1）埃迪卡拉纪（最新的前寒武纪）大型生物群出现在大约 5.7 亿年前的化石记录中，是一组具有早已灭绝的身体结构的生物体，但越来越多的证据表明，表明至少其中一些代表了古代非对称动物的遗骸。由于它们奇怪的解剖结构，它们通常不被纳入动物早期进化史的研究中，因此仍然是房间里的大象。我打算研究最年轻的埃迪卡拉大型生物群——erniettomorphs——它们是一组由连续重复的管组成的生物体——并且是最神秘的生物群之一，对于它们是什么或实际上不是什么还没有达成共识。我将使用我之前设计的方法，通过分析这些生物体如何生长和发育来研究它们的亲和力。我还将通过实地工作和研究博物馆藏品相结合，建立与其他动物（如果合适的话）相关的演化轨迹，以便弄清楚它们何时停止创新（改变它们的身体结构）以及何时灭绝。2 ）海绵通常被认为是最古老的动物谱系，但被广泛接受的最古老的海绵体化石的年龄仅为寒武纪。然而，有许多假定的埃迪卡拉海绵可能会在某种程度上扩展化石记录，使其更符合分子预期。我将使用大型照片数据集和新的未发表的野外标本重新检查这些化石的形态，以评估它们是否可能代表古代海绵。我还将使用计算流体动力学（一种模拟生物体周围流体流动的技术）来评估这些化石的解剖结构是否允许它们像活海绵一样发挥作用。如果这些化石中的任何一个可能是古代海绵，我会将它们与其他更年轻的海绵化石一起纳入形态系统发育分析中，以了解海绵生命树。然后我会将这些解剖学和化石年龄数据与 DNA 数据整合起来，以建立对海绵年龄的最严格的估计。 3）我将把上述数据与之前收集的埃迪卡拉大型生物群和刺胞动物（包含海葵、珊瑚和水母的群体）的其他成员的数据结合起来，以询问非两侧对称动物的解剖学变化速度是否确实更快晚前寒武纪（埃迪卡拉纪）或符合寒武纪爆发假说的预期。