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体生物多样性的进化。在数百万年的时间里，物种出现，变化，产生新的物种，然后灭绝。有明确的证据表明，这些事情发生的速度在物种之间和随着时间的推移而变化：生物多样性在不同生物群体中的分布太不均匀，以至于它们都以同样的方式多样化，化石记录表明，有些时候灭绝的风险特别高。然而，事实证明，很难确切地弄清楚为什么有些物种繁荣而另一些物种灭绝，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，因此可以将物种的数量与特定特征联系起来，比如体型小或能够飞行。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关于塑造生物多样性的过程如何随时间变化的直接信息。化石记录有关于过去的直接信息，但它往往过于零碎，无法告诉我们更多关于单个物种和谱系水平的详细过程。在过去的6500万年里，南极有孔虫可能是所有有孔虫中最好的化石记录。这些单细胞的，通常是美丽的，生物体在世界各地的海洋中大量存在。几千万年来，数十亿个个体像下雨一样落在海床上，通常形成厚厚的沉积物。深入这些沉积物就像回到有孔虫进化的时代，化石的数量之多使我们有可能以无与伦比的细节重建它们的历史。它们的进化关系可以拼凑在一起，每个物种的特征：物理尺寸可以测量，生态学可以从化学分析中推断。沉积物和其他数据来源也告诉我们每个化石的生活时间，以及它的世界是什么样的。这些信息的结合使我们有可能以前所未有的细节来理解有孔虫进化的“规则”。在过去的6500万年里，物种形成和灭绝的速度是如何变化的？高多样性会抑制物种形成，导致灭绝，两者都不会，还是两者兼而有之？个体物种在下一段时间内形成物种或灭绝的概率取决于它们的年龄吗？哪些生态特征决定物种形成和灭绝率？体型变大的趋势是否仅仅源于物种内部的变化，或者体型也会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进化的，它们的进化速度与多样化的速度有关吗？这些“规则”在时间上有多恒定？当灭绝率高时，与正常情况相反，或者当气候变化时，与稳定时，是否有不同的规则？这些问题中的一些已经在某些生物群体中得到解决，但浮游有孔虫提供了一个机会，以获得一个综合的概述如何在自然环境中出现大规模的进化模式。这样的概述对所有研究宏观进化的研究人员来说都是有价值的，因为在大多数其他生物群体中，不可能严格地研究这些问题：对一个“模型”系统有一个详细的了解，这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.