Morphometric comparison of three Southern Ocean Fragilariopsis species@en

While attempting to assemble a reference image set of Southern Ocean diatoms for training automatic classification algorithms, we encountered numerous specimens which we were unable to classify unequivocally into one of three highly similar Fragilariopsis species. Problems about the delimitation of these species were also raised at the last Polar Marine Diatom Workshop in 2015 in Salamanca. The present study originated from these two sources. Using semi-automated microscopy and image analyses, we assembled a set of 501 specimen images and accompanying morphometric data, and 12 members of the polar marine diatomist community contributed their identification of these specimens independently from each other. After comparing the identification results themselves, we used the morphometric features extracted in an attempt to clarify the nature of morphometric distinction of the three taxa in uni-and bivariate analyses, and performed multivariate classification experiments and tested their agreement with expert consensus opinion. Beyond the specific insights into morphometric distinction of the studied taxa, our study also highlights some of the more generic challenges and possibilities of research at the interface between automatic identification and traditional taxonomy.本研究最初旨在构建一套南大洋硅藻参考图像集，用于训练自动分类算法，过程中发现大量标本无法明确归类至3种形态极为相似的脆杆藻属（Fragilariopsis）物种。2015年于萨拉曼卡举办的末次极地海洋硅藻研讨会上，上述物种的分类界定难题也曾被提出。本研究正是基于这两项契机展开。研究采用半自动显微镜技术与图像分析手段，构建了包含501份标本图像及配套形态测量数据的数据集；同时邀请12位极地海洋硅藻研究领域的专家，对这些标本开展独立分类鉴定。在比对所有鉴定结果后，我们通过单变量与双变量分析提取形态测量特征，以厘清这3个分类群的形态差异本质；同时开展多变量分类实验，并验证其与专家共识意见的一致性。除了针对所研究分类群的形态差异获得专属认知外，本研究还揭示了自动识别与传统分类学交叉领域研究中普遍存在的挑战与潜在方向。