Macroevolution in planktonic foraminifera

该项目旨在提供比迄今为止更详细、更准确和更全面的了解，了解生态和环境如何在很长一段时间内塑造一组生物的生物多样性的演变。在数百万年的时间里，物种不断涌现、变化，催生新的物种，然后灭绝。有明确的证据表明，随着物种和时间的推移，这些事情发生的速度会有所不同：生物多样性在不同的有机体群体中分布得太不均匀，以至于它们都以同样的方式多样化，化石记录表明，有时灭绝的风险特别高。然而，事实证明，很难准确地弄清楚为什么有些物种兴旺发达，有些物种灭绝，或者为什么有些时候更好，有些时候更糟。对于大多数群体来说，我们最了解当今的多样性，所以可以将物种的数量与特定的特征联系起来，比如体型较小或能够飞行。然而，这样的分析并不能告诉我们这些特征是否会影响物种形成的速度、灭绝的速度，或者两者兼而有之。它们也不能为我们提供形成生物多样性的过程随着时间的推移而发生变化的直接信息。化石记录有关于过去的直接信息，但它往往太不完整，无法告诉我们在单个物种和谱系层面上的详细过程。浮游有孔虫可能是过去6500万年来最好的化石记录。这些单细胞生物通常是美丽的，在世界各地的海洋中大量发现。数千万年来，数十亿人像雨点一样落在海床上，往往形成了厚厚的沉积物。深入到这些沉积物中就是回到了孔洞演化的时间，而化石的绝对数量使得以无与伦比的细节重建它们的历史成为可能。它们的进化关系可以拼凑在一起，每个物种都有特征：物理尺寸可以测量，生态可以通过化学分析推断。沉积物和其他数据来源也告诉我们每一块化石的生活时间，以及它的世界是什么样子的。这种信息的结合使我们有可能以前所未有的详细程度理解支配形态演变的“规则”。在过去的6500万年里，物种形成和灭绝的速度发生了怎样的变化？高度的多样性是否会抑制物种形成、导致物种灭绝、两者都不会，或者两者兼而有之？个别物种在下一段时间内形成物种或灭绝的可能性取决于它们的年龄吗？哪些生态特征决定了物种形成和灭绝的速度？更大体型的趋势是否仅仅源于物种内的变化，或者体型是否也影响物种形成和灭绝的速度？形态特征是如何随着时间的推移而演变的，它们的演变速度是否与多样化的速度有关？这些“规则”在时间中保持了多长时间？有没有不同的规则，当物种灭绝速度很高，而不是正常的；或者当气候变化，而不是稳定的时候？其中一些问题以前已经在某些生物体群体中得到了解决，但浮游有孔虫提供了一个机会，以获得关于大规模进化模式如何在自然环境中产生的综合概述。这样的概述对于所有研究宏观进化的研究人员来说都是有价值的，因为不可能在大多数其他有机体群体中严格地看待大多数这些问题：拥有一个‘模型’系统的详细图景也将有助于研究其他群体的研究人员。

This project aims to provide a more detailed, precise and comprehensive understanding than has so far been possible of how ecology and environments shape the evolution of biodiversity in a group of organisms over a long period of time. Over millions of years, species arise, change, give rise to new species and then go extinct. There is clear evidence that the speed with which these things happen varies among species and over time: biodiversity is too unevenly spread among different groups of organisms for them all to have been diversifying in the same way, and the fossil record shows that there have been times when the risk of extinction has been particularly high. However, it has proved very hard to work out exactly why some species have thrived and others died out, or why some times are better and others worse. For most groups, we know most about present-day diversity, so can relate numbers of species to particular characteristics, like small size or being able to fly. Such analyses, however, don't tell us whether those characteristics affect the rate at which species are formed, the rate of extinction, or both. Nor can they give us direct information about how the processes shaping biodiversity have changed over time. The fossil record has direct information about the past, but it is often too patchy to tell us much about detailed processes at the level of individual species and lineages. The planktonic foraminifera have probably the best fossil record of any group over the past 65 million years. These single-celled, often beautiful, organisms are found in vast numbers in seas throughout the world. For tens of millions of years, billions of individuals have rained down on the sea bed, often forming thick sediments. To go down into these sediments is to go back in time in foram evolution, and the sheer numbers of fossils make it possible to reconstruct their history in unparalleled detail. Their evolutionary relationships can be pieced together, and each species characterised: physical dimensions can be measured, and ecology inferred from chemical analysis. The sediments, and other sources of data, also tell us when each fossil lived, and what its world was like. This combination of information makes it possible to understand in unprecedented detail the 'rules' governing foram evolution. How have rates of speciation and extinction changed through the last 65 million years? Does high diversity suppress speciation, cause extinction, neither, or both? Do individual species' probabilities of speciating or going extinct in the next slice of time depend on how old they are? Which ecological characters shape speciation and extinction rates? Does the tendency towards larger size stem solely from within-species changes, or does size affect speciation and extinction rates too? How do morphological characters evolve over time, and is the rate of their evolution tied up with rates of diversification? And how constant have these 'rules' been through time? Are there different sets of rules when extinction rates are high, as opposed to normal; or when climate is changing, as opposed to stable? Some of these questions have been tackled before in some groups of organisms, but planktonic forams provide the opportunity to gain a synthetic overview of how large-scale patterns in evolution arise in natural environments. Such an overview would be valuable to all researchers looking at macroevolution, because it is not possible to look at most of these questions rigorously in most other groups of organisms: having a detailed picture of one 'model' system will help researchers working on other groups too.