Combined genetic, morphological and ecological approaches to reduce uncertainty in palaeoclimate reconstructions using benthic foraminifers

对我们来说，弄清过去气候是如何变化的是非常重要的。如果不知道，我们就无法预测未来的气候变化。在过去的几十年里，我们才收集了全球气候变量的系统测量数据，但我们需要知道它在更长时间内的变化情况。我们特别需要了解北大西洋陆架海的这一点，这些海目前正在经历加速的气候变化。这些地区的海洋沉积层含有微生物的骨骼，可以提供有关过去气候的信息。特别是底栖有孔虫生活在这些浅海栖息地，它们的微观方解石壳随着时间的推移而积累，提供了过去环境的高分辨率记录。特定物种的群落（组合）与陆架海的区域生境有关，这种关系适用于沉积物时间片中发现的类似组合（转移函数）。有孔虫还将它们生长的海水的物理和化学特征融入它们的外壳中。这可以作为一个地球化学的“代用品”来重建他们过去生活的环境。所有这些过去的气候重建都是基于这样的假设，即单一物种的外壳是在相同的环境条件下建造的。使用活有孔虫中独特的DNA标记，我们知道这并不总是正确的。个体形态种有时代表几种不同的遗传类型（基因型），它们可能适应同一形态种范围内的不同环境。很可能是不同的物种。科学家们在不知不觉中分析了不同物种的混合物，因为它们看起来非常相似（神秘物种）。这将在传递函数法和地球化学代用指标的数据中引入噪声和可能的误差。为了克服这一点，我们建议基因型的所有重要的底栖形态物种用于过去的气候重建整个区域的栖息地（地理省）的中高纬度的东北大西洋。我们将在来自挪威和冰岛的四个项目合作伙伴的帮助下进行采样。我们还必须记住，随着季节的变化，这些地区会经历各种各样的环境条件。为了解决这个问题，我们将从正在进行季节性研究的地区采集样本，以了解不同的基因型是否会随着环境条件的变化而出现。这项研究的核心是对贝壳形状进行广泛的形态学研究，以确定我们是否可以找到细微的差异，以帮助识别现代海洋中的新基因型，最重要的是，在化石记录中。我们希望从遗传学和形态学上确定东北大西洋过去气候重建所用的所有重要底栖形态物种，以制定统一的分类方案。从我们的高分辨率采样，我们将能够产生一个新的生物区分布图，为今天东北大西洋/北极。我们将发现“通才”物种是否真的占据了不同的生物区，或者代表了一系列具有不同生态的不同神秘物种。发现可识别的新物种将提高我们对生物区如何随着冰川周期的到来和消失而向北/南迁移的理解。随着季节的变化，不同的神秘物种会出现在同一个地方吗？对它们的认识将有助于探索化石记录中的季节性。同一物种的有孔虫壳在不同的环境中会有不同的形状吗？确认将提供当前和过去特定环境条件的证据。现在和过去之间的这种联系也提供了重要的线索，说明这些动态海洋环境的极端变化如何影响物种的生存，并推动它们随着时间的推移而进化。

It is very important for us to find out how climate changed in the past. Without knowing, we cannot predict how the future climate might behave. Global, systematic measurements of climatic variables have only been collected over the last few decades but we need to know how it varied through longer periods of time. We particularly need to know about this in the North Atlantic shelf seas which are currently experiencing accelerating climate change. The layers of ocean sediments in these regions contain the skeletons of microscopic organisms which can provide information about past climate. Benthic foraminifers in particular live in these shallow ocean habitats and their microscopic calcite shells accumulate through time providing a high resolution record of past environments. Communities of specific species (assemblages) are associated with the regional habitats of the shelf seas and this relationship is applied to similar assemblages found in time slices in the sediments (transfer functions). Forams also incorporate into their shells the physical and chemical signatures of the seawater in which they grow. This can be used as a geochemical 'proxy' to reconstruct the past environment in which they lived. All these past climate reconstructions are based on the assumption that the shells of a single species were constructed in the same range of environmental conditions. Using a unique DNA marker in living forams, we know that this is not always true. Individual morphospecies sometimes represent several distinct genetic types (genotypes) which may be adapted to different environments within a morphospecies range. It is highly likely that these are different species. Scientists are unknowingly analysing a mixture of different species because they look very similar (cryptic species). This will introduce noise and possible error into the data of both transfer function methods and geochemical proxies. To overcome this, we propose to genotype all the important benthic morphospecies used for past climate reconstruction throughout the regional habitats (biogeographic provinces) of the mid to high latitudes of the northeast Atlantic. We will sample these with the help of our four project partners from Norway and Iceland. We also have to bear in mind that these regions experience a wide range of environmental conditions as the seasons change. To address this, we will take samples from regions where seasonal studies are being carried to find out whether different genotypes appear as the environmental conditions change. Central to this study will be an extensive morphological investigation of shell shape to find out whether we can find subtle differences to help recognise the new genotypes in the modern ocean and most importantly, in the fossil record. We hope to genetically and morphologically define all important benthic morphospecies used for past climate reconstruction in the North East Atlantic to produce a unified classification scheme. From our high resolution sampling, we will be able to produce a new bioprovince distribution map for the present day northeast Atlantic/Arctic. We will discover whether 'generalist' species really occupy different bioprovinces or represent a series of different cryptic species with different ecologies. Finding identifiable new species will improve our understanding of how bioprovinces have migrated North/South as the glacial cycles have come and gone. Do different cryptic species appear in the same place as the seasons change? Their recognition would allow the exploration of seasonality in the fossil record. Do foram shells of the same species have a different shape in different environments? Confirmation will provide evidence of specific environmental conditions in the present day and in the past. This link between present and past also provides important clues about how extreme changes in these dynamic marine environments affect the survival of species and drive their evolution through time.