Palaeodiversity and formation counts: redundancy or bias?
Palaeodiversity and formation counts: redundancy or bias?
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古多样性和地层计数：冗余还是偏差？
DOI：
10.1111/pala.12191
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发表时间：
2015-11-01
期刊：
影响因子：
2.6
通讯作者：
Benton, Michael J.
中科院分区：
文献类型：
--
作者：
Benton, Michael J.
古生物学中的一个关键问题是，从表面上看，化石记录是否足以代表随着时间推移的真实多样性模式。一些评估数据质量的方法依赖于通常观察到的古生物多样性和含化石地层数量随时间的协变，基于这样的假设，即含有化石的地层数量或多或少地驱动着多样性;但是如果多样性驱动着地层呢？对早期四足动物（泥盆纪-侏罗纪）和恐龙这两个化石记录的仔细研究表明，新的分类群和新的含化石地层之间的关系如何随着研究时间的推移而变化。最初，每一个新发现都代表一个新的含化石地层，发现遵循富矿带模式（化石驱动地层）。在世界上未开发的地区，新的分类群经常在新的区域/地层中被发现。只有经过一段时间后，在欧洲和北美等经过充分探索的大陆，收集风格才转变为探索新地层和重新采样已知的含矿地层的混合。恐龙的数据最令人震惊，三叠纪-侏罗纪记录主要包括来自欧洲和北美的发现，新的地层发现在1914年达到了它们的半衰期。这与白垩纪形成鲜明对比，白垩纪主要是欧洲和北美以外地区的快速增长的发现，这些新大陆的形成半衰期是1986年，表明50%的新白垩纪含化石地层是在过去30年才被发现的。含化石地层与古生物多样性之间的关系则结合了三种不同数量的信号，反映了原始的多样性（不同地层中特定类群的相对丰度）、冗余（由于新的化石发现而产生的新的含化石地层）和取样（对新的含化石地层的勘探强度，以及在已经取样的地层中的搜索强度）。至少对于脊椎动物化石来说，各种地层的计数都不能很好地预测采样，例如，拉格斯塔滕的富矿样品，如中国的义县组：成千上万的标本，几十个物种，但被算作一个地层。这些观察结果表明，地层计数不能被视为一个无偏的抽样度量。
A key question in palaeontology is whether the fossil record taken at face value is adequate to represent true patterns of diversity through time. Some methods of assessing data quality have depended on the commonly observed covariation of palaeodiversity and fossiliferous formation counts through time, based on the assumption that the count of formations containing fossils, to a greater or lesser extent, drives diversity; but what if diversity drives formations? Close study of two fossil records, early tetrapods (Devonian-Jurassic) and dinosaurs, shows how the relationship between new taxa and new fossiliferous formations varies through research time. Initially, each new find represents a new fossiliferous formation and discovery follows the bonanza' model (fossils drive formations). In unexplored parts of the world, new taxa are identified frequently in new regions/formations. Only after time, in well-explored continents such as Europe and North America, does collecting style switch to a mix of exploration for new formations and re-sampling of known fossiliferous formations. Data are most striking for dinosaurs, where the Triassic-Jurassic record largely comprises finds from Europe and North America, where new formation discoveries reached their half-life in 1914. This contrasts with the Cretaceous, which is dominated by rapidly rising discoveries from regions outside Europe and North America and the formation half-life for these new' lands is 1986, showing that 50% of new Cretaceous dinosaur-bearing formations were identified only in the past 30years. The relationship between dinosaur-bearing formations and palaeodiversity then combines three signals in variable amounts, reflecting the original diversity (relative abundances of particular taxa in different formations), redundancy (new fossiliferous formations accruing because of new fossil finds) and sampling (intensity of exploration for new fossiliferous formations, and of search within already-sampled formations). For fossil vertebrates at least, formation counts of various kinds are poor predictors of sampling, missing, for example, the bonanza samples of Lagerstatten such as the Yixian Formation in China: thousands of specimens, dozens of species, but counted as one formation. These observations suggest that formation count cannot be regarded as an unbiased metric of sampling.