背景:考古植物学家和古生态学家广泛使用几何形态计量学来识别植物蛋白石植物。特别是当应用于从封闭环境中检索到的浓度的植物石组合时,与来自参考材料的类似数据相比,来自考古植物的形态测量数据可能允许分类学归属。观察者变异是植岩形态计量学的一个方面,很少受到关注,但可能是一个重要的误差来源。因此导致植物残留的潜在错误识别。
方法:为了研究植物石形态计量学中观察者之间和观察者之间的变化,来自不同实验室的八名研究人员(观察员)测量了三种植物形态型的50个样本,双叶,大泡状扇形和细长树突状,三次,在国际植物形态计量学委员会(ICPM)的主持下。
方法:通过手动数字化照片中的植物石轮廓(面具),为每个植物石收集了17个大小和形状变量的数据,然后用开源形态测量软件测量面罩。
结果:观察者间的变化与所有观察者的平均值相差0%至23%。观察者内的变化与每周单个观察者的平均值相差0%至9%。在没有经验的研究人员中,观察者之间和观察者之间的差异通常较高。
结论:缩放错误是变异的主要原因,更多发生在经验不足的研究人员身上,这可能与熟悉数据收集有关。结果表明,通过为设备提供清晰的指示和培训,可以大大减少观察者之间和观察者内部的变化,照片捕获,软件,数据收集和数据清理。在本文中,ICPM提供了将变化降至最低的建议。自动数据收集的进步最终可能会减少观察者之间和观察者内部的变化,但是在这成为惯例之前,ICPM建议植岩形态计量分析遵循标准化准则,以确保测量的植岩变量是准确的,不同研究人员和实验室之间的一致性和可比性。
BACKGROUND: Archaeobotanists and palaeoecologists extensively use geometric morphometrics to identify plant opal phytoliths. Particularly when applied to assemblages of phytoliths from concentrations retrieved from closed contexts, morphometric data from archaeological phytoliths compared with similar data from reference material may allow taxonomic attribution. Observer variation is one aspect of phytolith morphometry that has received little attention but may be an important source of error, and hence cause of potential misidentification of plant remains.
METHODS: To investigate inter- and intra-observer variation in phytolith morphometry, eight researchers (observers) from different laboratories measured 50 samples each from three phytolith morphotypes, Bilobate, Bulliform flabellate and Elongate dendritic, three times, under the auspices of the International Committee for Phytolith Morphometrics (ICPM).
METHODS: Data for 17 size and shape variables were collected for each phytolith by manually digitising a phytolith outline (mask) from a photograph, followed by measurement of the mask with open-source morphometric software.
RESULTS: Inter-observer variation ranged from 0 to 23% difference from the mean of all observers. Intra-observer variation ranged from 0 to 9% difference from the mean of individual observers per week. Inter- and intra-observer variation was generally higher among inexperienced researchers.
CONCLUSIONS: Scaling errors were a major cause of variation and occurred more with less experienced researchers, which is likely related to familiarity with data collection. The results indicate that inter- and intra-observer variation can be substantially reduced by providing clear instructions for and training with the equipment, photo capturing, software, data collection and data cleaning. In this paper, the ICPM provides recommendations to minimise variation.Advances in automatic data collection may eventually reduce inter- and intra-observer variation, but until this is common practice, the ICPM recommends that phytolith morphometric analyses adhere to standardised guidelines to assure that measured phytolith variables are accurate, consistent and comparable between different researchers and laboratories.