Foraminiferal genotype adaptation and their potential to enhance palaeoceanographic proxies

浮游有孔虫(有孔虫)是生活在海洋浮游生物中的一类重要的单细胞生物。它们坚硬的碳酸钙外壳印有它们生长环境的化学记录，作为微化石保存在它们数百万年积累的沉积物中。研究人员使用它们来重建过去的海洋环流和气候，方法是假设一种形态物种(由形状定义的物种)的所有贝壳都是在相同的环境范围内构建的。在活着的有孔虫中使用了一种独特的DNA标记，我已经能够证明这不是真的。每个形态种通常有几个不同的遗传类型(基因类型)，许多都适应不同的环境。因此，基因类型在不同的环境中相互建造外壳，科学家们在不知不觉中使用了不同类型的混合物。对于使用化石贝壳中的化学证据来了解这些地区过去的气候变化的研究来说，这是一个不可预见的问题。在我的高级研究员期间，我的主要任务是评估重要形态物种的遗传变异和新鉴定的基因类型的不同适应。到目前为止，我已经收集了从北极高地到南极的数千个样本，目标是研究过去气候变化的科学家特别感兴趣的地区。有孔虫可以在洋流中被带到很远的地方，尽管扩散似乎没有什么障碍，但不同的基因型别确实有不同的适应能力，并不是生活在任何地方。有些人更适应热或冷，另一些人则适应不同数量或类型的食物。我发现，生活在两极地区的相同形态物种在大约200万年前寒冷的冰川期开始时发生了基因分裂。南极的冰川后来也再次分化，其中一只适应了海冰的极端环境，而另一些则发现自己被留在了后面，被隔绝在最后一次冰川时期后的冷流中。所有这些知识告诉我们，生命是如何在海洋中分裂成不同的物种的，我在领先的期刊上提醒了科学家们许多这些新的进化发现。对于过去的气候重建，将几种基因组合在一起必然会给研究人员的计算和气候模型带来误差。我关于高纬度海洋寒冷地区生物有孔虫遗传多样性和生态的证据突显并解决了其中一些问题。我为科学家们提供了新的方法，通过利用这些地区不断变化的有孔虫贝壳的形状来提高化石记录解释的准确性。热带和亚热带水域在地球气候系统中发挥着同样重要的作用，现在调查热带和亚热带水域的风致上升区，以确定这些截然不同的生态系统的基因结构，是目前的一个高度优先事项。我建议在印度洋和太平洋的三次不同航程中对这些地区进行采样，以确定哪些基因类型生活在那里，以及它们生活在特定的水柱条件下。我将结合不同深度的基因鉴定和对它们在生命周期中产生的不同壳层的高分辨率化学分析。将对基因型壳形状进行广泛的调查，以便于在化石记录中识别它们。提高当今低纬数据的分辨率，了解贝壳地球化学与基因生长的物理环境之间的关系，对于过去的气候模型至关重要。这项工作将与一支强大的专家团队合作完成，他们致力于重建英国和国外的过去气候。此外，正在汇编所有基因分型标本及其位置的新数据库，完成后将提供给科学界使用。

Planktonic foraminifers (forams) are an important group of single-celled organisms that live in the marine plankton. Their hard shells of calcium carbonate, imprinted with a chemical record of the environment in which they grew, are preserved as microfossils in the sediments where they have accumulated over millions of years. Researchers use them to reconstruct ocean circulation and climate in the past by assuming that all shells of a morphospecies (species defined by shape) were constructed within the same environmental range. Using a unique DNA marker in living forams, I have been able to show that this is not true. Each morphospecies often has several distinct genetic types (genotypes) and many are adapted to different environments. Genotypes therefore build their shells in different environments from one another and scientists are unknowingly using a mixture of different types. This is an unforeseen problem for researches using chemical evidence from fossil shells to understand past climate changes in these regions . During my Advanced Fellowship, my principle task has been to assess genetic variation within important morphospecies and the different adaptations of newly identified genotypes. I have collected thousands of samples to date from the high Arctic to the Antarctic, targeting regions of special interest to scientists who investigate changes in the past climate. Forams can be carried over great distances in the ocean currents and although there seem to be few barriers to dispersal, individual genotypes do have different adaptations and do not live everywhere. Some are more adapted to the heat or cold, others to different amounts or types of food. I have discovered that the same morphospecies living in both polar regions became genetically split around two million years ago when the cold glacial period began. The Antarctic ones also diverged again later and one become adapted to live in the extreme environment of the sea-ice while others have found themselves left behind, isolated in a cold current following the last glacial period. All this knowledge tells us about how life splits up into different species in the ocean and I have alerted scientists to many of these new evolutionary discoveries in leading journals. For past climate reconstruction, pooling several genotypes together must impose error into researcher's calculations and climate models. My evidence on the genetic diversity and ecology of living forams in the cold regions of the high latitude oceans has highlighted and solved some of these problems. I have provided scientists with new ways of improving accuracy in fossil record interpretation by utilising the changing shapes of foram shells in these regions. It is now a high priority to investigate the wind driven upwelling regions of the tropical and subtropical waters which play an equally vital role in earth's climate system to determine the genotypic structure of these quite different ecosystems. I propose to sample these regions during three separate cruises in the Indian and Pacific Oceans to determine which genotypes live there and the specific water column conditions they live in. I will combine genotyping at different depths with high resolution chemical analyses of the different layers of their shell produced during their life cycle. An extensive investigation into genotype shell shape will be carried out to facilitate their identification in the fossil record. Improving the resolution of present day low latitude data on the relationship between shell geochemistry and the physical environment in which genotypes grow is vital for past climate modelling. This work will be done in collaboration with a strong team of experts who work on the reconstruction of past climate both in the UK and abroad. In addition, a new data base of all genotyped specimens and their location is being compiled which will be made available for use by the scientific community when complete.