Data from: A potential pitfall in studies of biological shape: does size matter?

1. The number of published studies using geometric morphometrics (GM) for analysing biological shape has increased steadily since the beginning of the 1990’s, covering multiple research areas such as ecology, evolution, development, taxonomy and palaeontology. Unfortunately, we have observed that many published studies using GM do not evaluate the potential allometric effects of size on shape, which normally require consideration or assessment This might lead to misinterpretations and flawed conclusions in certain cases, especially when size effects explain a large part of the shape variation. 2. We assessed, for the first time and in a systematic manner, how often published studies that have applied GM consider the potential effects of allometry on shape. 3. We reviewed the 300 most recent published papers that used GM for studying biological shape. We also estimated how much of the shape variation was explained by allometric effects in the reviewed papers. 4. More than one third (38%) of the reviewed studies did not consider the allometric component of shape variation. In studies where the allometric component was taken into account, it was significant in 88% of the cases, explaining up to 87.3% of total shape variation. We believe that one reason that may cause the observed results is a misunderstanding of the process that superimposes landmark configurations, i.e. the Generalized Procrustes Analysis, which removes isometric effects of size on shape, but not allometric effects. 5. Allometry can be a crucial component of shape variation. We urge authors to address, and report, size effects in studies of biological shape. However, we do not propose to always remove size effects, but rather to evaluate the research question with and without the allometric component of shape variation. This approach can certainly provide a thorough understanding of on how much size contributes to observed shaped variation.1. 自20世纪90年代初以来，采用几何形态测量学（geometric morphometrics, GM）分析生物形态的已发表研究数量持续增长，研究领域覆盖生态学、进化生物学、发育生物学、分类学与古生物学。遗憾的是，我们发现诸多采用GM的已发表研究并未评估体型对形态的潜在异速生长效应，而此类效应通常是需要考量或评估的内容。在某些情形下，这可能会导致解读偏差与错误结论，尤其是当体型效应能够解释大部分形态变异时。 2. 我们首次以系统性的方式，评估了采用GM的已发表研究中，考量体型对形态潜在异速生长效应的研究占比。 3. 我们对最新发表的300篇采用GM开展生物形态研究的论文进行了综述，并估算了所综述论文中异速生长效应可解释的形态变异比例。 4. 本次综述的研究中有超过三分之一（38%）未考量形态变异的异速生长组分。在纳入异速生长组分的研究中，88%的案例显示异速生长效应显著，其可解释的形态变异最高可达总变异的87.3%。我们认为，导致这一结果的原因之一，可能是研究者对地标配置叠加流程——即广义Procrustes分析（Generalized Procrustes Analysis）——存在误解：该流程仅可移除体型对形态的同速生长效应，而非异速生长效应。 5. 异速生长效应可能是形态变异的关键组分。我们呼吁研究者在生物形态研究中处理并报告体型效应。但我们并非主张始终移除体型效应，而是建议在纳入与排除形态变异异速生长组分的两种情境下，分别对研究问题进行评估。该方法无疑可帮助我们全面明晰体型对观测到的形态变异的贡献占比。