Sample size and sampling error in geometric morphometric studies of size and shape
Sample size and sampling error in geometric morphometric studies of size and shape
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DOI：
10.1007/s00435-007-0036-2
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发表时间：
2007-08-01
期刊：
影响因子：
1
通讯作者：
Elton, Sarah
中科院分区：
文献类型：
--
作者：
Cardini, Andrea;Elton, Sarah
几何形态学研究在系统学和古生物学中变得越来越普遍。由于无法分析的材料，此类研究中的样本通常很小。但是，很少有研究试图评估抽样误差对分析结果的影响。在这里，使用重复的随机选择实验经验解决此问题，以从与400个Vervet Monkey（Cercopithecus aethiops）头骨相似的原始数据集逐渐构建较小的样本。在几何形态计量研究中常用的尺寸和形状参数（包括平均大小和形状，大小和形状方差，异形轨迹的角度，异形轨迹的角度），首先在原始样本中，然后在随机的子样本中估算。然后将估计值进行比较，以指示每个参数的最小值样本量是多少。即使在相对较小的样本中，平均大小，大小的标准偏差和形状方差也相当准确。相比之下，静态异形轨迹之间的平均形状和角度受到采样误差的强烈影响。如果在其他群体中得到证实，我们的发现可能对当前和化石物种中形态变异的研究可能具有重大影响。通过进行稀疏分析，例如我们研究中提出的稀疏分析，可以轻松地为形态学师提供有关简单但至关重要的因素（例如样本量）如何改变其研究结果的重要线索。
Geometric morphometric studies are increasingly becoming common in systematics and palaeontology. The samples in such studies are often small, due to the paucity of material available for analysis. However, very few studies have tried to assess the impact of sampling error on analytical results. Here, this issue is addressed empirically using repeated randomized selection experiments to build progressively smaller samples from an original dataset of similar to 400 vervet monkey (Cercopithecus aethiops) skulls. Size and shape parameters (including mean size and shape, size and shape variances, angles of allometric trajectories) that are commonly used in geometric morphometric studies, are estimated first in the original sample and then in the random subsamples. Estimates are then compared to give an indication of what is the minimum desirable sample size for each parameter. Mean size, standard deviation of size and variance of shape are found to be fairly accurate even in relatively small samples. In contrast, mean shapes and angles between static allometric trajectories are strongly affected by sampling error. If confirmed in other groups, our findings may have substantial implications for studies of morphological variation in present and fossil species. By performing rarefaction analyses like those presented in our study, morphometricians can be easily provided with important clues on how a simple but crucial factor like sample size can alter results of their studies.