Survival and re-diversification of pentameride brachiopod fauna from Late Ordovician to early Silurian

晚奥陶世至早志留世五肢腕足动物群的生存和再多样化

• 批准号: RGPIN-2019-04747
• 负责人: Jin, Jisuo
• 金额: $ 3.33万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714907
• 关键词: Survival; re; diversification; pentameride; brachiopod

As a group of dominant marine sea shells in the Ordovician and Silurian periods (485419 million years ago), brachiopods experienced drastic diversity fluctuations through greenhouse-icehouse climate changes in the Late Ordovician-early Silurian. The Pentameridine group underwent a moderate radiation during the Late Ordovician but became nearly extinct during the Late Ordovician Mass Extinction, reduced to a single genus Brevilamnulella. By the early Silurian, pentameride radiated rapidly to dominate the shallow seas. Thus the origin and early evolution of the pentameridines constituted a striking case of near total extinction but rapid re-diversification. Earliest Silurian pentamerides showed rapid morphological transformations to adapt to a wide range of water depth and substrate conditions, represented by three major groups (the virgianids, stricklandiids, and clorindids). The oldest Stricklandia and Clorinda in the earliest Silurian show morphological similarities to Brevilamnulella, with younger stricklandioids evolving towards a large shell with a wide hingeline to adapt to relatively deep-water, soft muddy substrate. The clorindioids retained a relatively small, globular shell to specialize in living in low-energy, deep-water, outer-shelf environment. The early Silurian diversification of pentamerides from Brevilamnulella is interpreted as rapid exploration of a wide range ecological niches from shallow, high-energy settings to deep and quiet outer-shelf environments, left largely “empty” by the Late Ordovician mass extinction event. The great morphological plasticity in earliest Silurian pentamerides has made it difficult to quantitatively study their initial diversification. This study will examine the morphological variability among the Hirnantian Brevilmnulella and the earliest Silurian pentamerides to determine their phylogenetic relationships among the ancestral Brevilamnulella and the earliest Silurian virgianids, stricklandioids, and clorindioids, and to explore the ecological factors related to speciation. To test the hypothesis that the extinction survivor Brevilamnulella gave rise to a multitude of pentameride brachiopods that became the dominant Silurian “sea shells”, research collaborations with several international colleagues will help gain access to key pentameride collections from Canada, the UK, North Greenland, and South China, ranging from the Late Ordovician to early Silurian. A multi-technique approach (serial sectioning, moulds and cast, and micro-CT scanning) will be used to build a reliable morphological database. The data will then be analyzed using multivariate and cladistic methods to reveal evolutionary trends, phylogenetic relationships, and paleoecological implications. This type of study will help shed light on the evolutionary processes when global biodiversity undergoes a drastic boom-bust-recovery cycle.

作为奥陶纪主导的志留纪（距今4854.19亿年前）的海洋贝壳类群，腕足动物在晚奥陶世-早志留世期间经历了温室-冰库气候变化的剧烈多样性波动，而五美利丁类群在晚奥陶世经历了中度辐射。但在奥陶纪晚期大灭绝期间几乎灭绝，到了早期，Brevilamnulella 只剩下一个属。志留纪，五美胺迅速辐射并统治了浅海，因此五美胺的起源和早期进化构成了一个几乎完全灭绝但迅速重新多样化的惊人案例。 最早的志留纪五聚体表现出快速的形态转变，以适应广泛的水深和底质条件，以三个主要类群（virgianids、striclandiids 和 clorindids）为代表，最早志留纪中最古老的 Stricklandia 和 Clorinda 显示出与 Brevilamnulella 的形态相似性。较年轻的斯特里克兰类进化为具有宽铰线的大壳，以适应相对深水、柔软的泥质基质。克罗林二类保留了相对较小的球状外壳，专门生活在低能量、深水、外陆架环境中。来自Brevilamnulella的五聚体的早期志留纪多样化被解释为从浅层、高水位快速探索广泛的生态位。能源设置转向深层而安静的外陆架环境，由于晚奥陶世大规模灭绝事件，该环境基本上“空无一人”。 最早志留纪五聚体的巨大形态可塑性使得定量研究其最初的多样化变得困难。本研究将检查赫南特布雷维姆努勒拉和最早的志留纪五聚体之间的形态变异，以确定它们的祖先布雷维拉姆努拉和最早的志留纪维吉安科之间的系统发育关系。 striclandioids 和 clorindioids，并探索与物种形成相关的生态因素。 为了验证灭绝幸存者 Brevilamnulella 产生了大量五胺腕足动物并成为志留纪主要“海贝壳”的假设，与几位国际同事的研究合作将有助于获得来自加拿大、英国、北格陵兰、以及华南地区，从奥陶纪晚期到志留纪早期，将采用多种技术方法（连续切片、模具和铸件以及显微 CT 扫描）。然后使用多元和分支方法对数据进行分析，以揭示进化趋势、系统发育关系和古生态学意义。此类研究将有助于揭示全球生物多样性急剧繁荣时的进化过程。 -萧条-恢复周期。