Quantifying Tiering of Marine Animal Forests Through Deep Time

海洋生态系统是地球上最重要的生态系统之一，塑造其起源的指导性生态和进化原则对于理解我们今天生活的世界至关重要。其中一个例子是海洋动物森林，这是一个三维的树冠，类似于水下森林，主要由具有生物矿化骨骼的无脊椎动物组成，如珊瑚和棘皮动物。这些生态系统是现代海洋生物多样性的摇篮，由于碳酸钙生物矿化剂的丰富，它们在碳循环中发挥着重要作用。尽管它们的意义，但是，宏观进化和宏观生态过程的起源和多样化的海洋动物森林没有很好的约束。特别是，分层，即群落内生物对空间的垂直细分，被认为是海洋动物林等海洋底栖群落多样化的驱动力，但很少对其进行量化。这种缺乏量化的现象阻碍了海洋动物森林在不同时空尺度上的比较，目前还缺乏一个统一的框架来促进分层及其对灭绝和现存海洋生态系统的影响的研究。为了了解海洋动物森林的起源和演变以及分层在构建这些群落中的作用，我们将设计一个定量的，跨学科的方法，使用尖端的统计方法和计算机模拟，以调查在海百合为主的海洋动物森林分层。海百合是底栖悬浮进食棘皮动物，自40多年前提出这一想法以来，一直是海洋底栖群落分层的典范。由于缺乏完整的海百合化石，因此它们是解决这一问题的理想群体。由于缺乏完整的海百合化石，对了解杯状体骨骼成分的生长和杯状体在海底以上的高度之间的关系是必要的，杯状体骨骼成分容纳了摄食附属物。最近在英国威尔特郡发现了一组保存异常完好的侏罗纪海百合化石，收藏在伦敦的自然历史博物馆，为开发、测试和基准测试一个统一的框架提供了完美的天然实验室，用于量化部分标本的分层。一旦实现了这一目标，我们将应用我们的新框架来量化一个古老的奥陶纪古群落和一个现代海百合为主的海洋动物森林的分层，以测试和确保我们的方法更广泛的适用性。我们的工作成果将提供深入了解海洋动物森林的生态和进化驱动因素。我们的新分析工具将广泛适用于海洋底栖生物群落，开辟环境科学研究的新方向。

Marine ecosystems are among the most important on planet Earth, and the guiding ecological and evolutionary principles that have shaped their origins are crucial to understand the world we live in today. One example of this are marine animal forests, which are three-dimensional canopies akin to underwater forests that are primarily comprised of invertebrate animals with biomineralized skeletons, like corals and echinoderms. These ecosystems are cradles of biodiversity in modern oceans, and they play an important role in the carbon cycle due to the abundance of calcium carbonate biomineralizers. Despite their significance, however, the macroevolutionary and macroecological processes underlying the origin and diversification of marine animal forests are not well constrained. In particular, tiering, the vertical subdivision of space by organisms within a community, has been proposed as a driver of diversification in marine benthic communities such as marine animal forests, but this has rarely been quantified. This lack of quantification has hampered comparisons of marine animal forests across different spatial and temporal scales, and a unified framework facilitating study of tiering and its effects on extinct and extant marine ecosystems is currently lacking.In order to understand the origin and evolution of marine animal forests and the role of tiering in structuring these communities, we will devise a quantitative, interdisciplinary approach using cutting-edge statistical methods and computer simulations to investigate tiering in crinoid-dominated marine animal forests. Crinoids are benthic suspension-feeding echinoderms, which have been the poster children for tiering in marine benthic communities since the initial conception of the idea over 40 years ago. They are thus the ideal group with which to tackle this topic.The development of a quantitative approach to tiering has classically been hindered by the absence of complete crinoid fossils, which are necessary to understand the relationship between growth of skeletal elements of the cup, which house the feeding appendages, and the height of the cup above the seafloor. The recent discovery of a new exceptionally-preserved assemblage of Jurassic fossil crinoids from Wiltshire, UK, housed at the Natural History Museum in London, offers the perfect natural laboratory to develop, test, and benchmark a unified framework for quantifying tiering from partial specimens. Once this has been achieved, we will apply our novel framework to quantify tiering in an older Ordovician palaeocommunity and a modern crinoid-dominated marine animal forest to test and ensure the wider applicability of our approach.The outcomes of our work will provide insight into the ecological and evolutionary drivers underlying marine animal forests. Our new analytical tools will be widely applicable to marine benthic communities, opening up novel directions of research in the environmental sciences.