Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data.
Bias and sensitivity in the placement of fossil taxa resulting from interpretations of missing data.
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DOI：
10.1093/sysbio/syu093
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发表时间：
2015-03
影响因子：
6.5
通讯作者：
Sansom RS
中科院分区：
文献类型：
--
作者：
Sansom RS
化石在进化背景下的效用取决于它们在系统发育框架中的准确位置，然而固有的和广泛的数据缺失使这成为问题。在石化过程中发生的复杂的埋藏过程使得区分缺失和非保存变得困难，特别是在特殊保存的软组织化石的情况下：化石中缺失的特定形态特征（如附属物、触手或神经）是因为它从未存在（系统发育缺失），还是碰巧没有被保存（埋藏丢失）？缺失的数据还没有在解释不存在的解剖背景下进行测试，也没有在亲和力的方向变化和偏差的背景下进行测试。在这里，完整的分类群，无论是模拟的还是经验的，都受到数据丢失的影响，因为现有的条目(1)被替换为缺失的(1)。S)或缺席(0)项。两者都会导致分类群从原来的位置向树根漂移。对于引入的缺失（替换了两个条目，占当前字符的6%），降档显著的绝对阈值极低。经验化石分类群的相反阈值也较低；两个缺失的条目被存在的条目所取代，导致化石分类群向树上漂移。因此，只有少数未保存的特征被解释为缺失，才会导致化石生物被错误地解释为比它们在生活中更原始。这种观察到的对非现存形态编码的敏感性给所有试图用化石来重建进化速率或解开形态变化序列的进化研究提出了一个问题。茎向滑移，即石化过程使生物体显得人为原始，似乎是一种普遍存在的问题现象，固有的缺失数据，即使不存在衰变偏差。因此，缺失的字符需要明确的理由和词法框架来支持他们的解释。
The utility of fossils in evolutionary contexts is dependent on their accurate placement in phylogenetic frameworks, yet intrinsic and widespread missing data make this problematic. The complex taphonomic processes occurring during fossilization can make it difficult to distinguish absence from non-preservation, especially in the case of exceptionally preserved soft-tissue fossils: is a particular morphological character (e.g., appendage, tentacle, or nerve) missing from a fossil because it was never there (phylogenetic absence), or just happened to not be preserved (taphonomic loss)? Missing data have not been tested in the context of interpretation of non-present anatomy nor in the context of directional shifts and biases in affinity. Here, complete taxa, both simulated and empirical, are subjected to data loss through the replacement of present entries (1s) with either missing (?s) or absent (0s) entries. Both cause taxa to drift down trees, from their original position, toward the root. Absolute thresholds at which downshift is significant are extremely low for introduced absences (two entries replaced, 6% of present characters). The opposite threshold in empirical fossil taxa is also found to be low; two absent entries replaced with presences causes fossil taxa to drift up trees. As such, only a few instances of non-preserved characters interpreted as absences will cause fossil organisms to be erroneously interpreted as more primitive than they were in life. This observed sensitivity to coding non-present morphology presents a problem for all evolutionary studies that attempt to use fossils to reconstruct rates of evolution or unlock sequences of morphological change. Stem-ward slippage, whereby fossilization processes cause organisms to appear artificially primitive, appears to be a ubiquitous and problematic phenomenon inherent to missing data, even when no decay biases exist. Absent characters therefore require explicit justification and taphonomic frameworks to support their interpretation.
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DOI：
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发表时间：
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影响因子：
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影响因子：
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