Lefebvre Keely E, Hamilton Paul B, Pick Frances R
Biology & Environmental Science, Centre for Advanced Research in Environmental Genomics, University of Ottawa, Ottawa, Ontario, Canada, K1N 6N5.
Research and Collections Division, Canadian Museum of Nature, P.O. Box 3443, Station D., Ottawa, Ontario, Canada, K1P 6P4.
J Phycol. 2017 Jun;53(3):680-702. doi: 10.1111/jpy.12537. Epub 2017 May 2.
Historically, a morphological species concept has applied shape subjectively in the delimitation of diatom species. This has led to confusion between taxa within the benthic diatom genus Neidium. Samples from Ontario, Quebec, Nova Scotia, Newfoundland (Canada) and New York (USA) were examined for Neidium taxa under LM and SEM. Fourier shape analysis showed that shape as a taxonomic character was not able to discern all species. Isolated individuals from the samples were amplified and sequenced for three chloroplast molecular markers (rbcL, psbC, and psbA) and one nuclear ribosomal molecular marker (18S). Phylogenetic reconstructions were completed with the concatenated chloroplast and 18S dataset using Maximum Likelihood and Bayesian analyses. The concatenated chloroplast dataset exhibited a species-level resolution phylogeny of Neidium taxa. The 18S dataset had a lower level of sequence divergence and was unable to differentiate between Neidium taxa. We present emended species descriptions and sequence data for four previously described species: Neidium sacoense, N. longiceps, N. fossum, and N. affine. We describe three novel species (Neidium lowei, N. promontorium, and N. potapovae) and identify two forms with unique molecular signatures. The distinguishing features of N. lowei are its size, valve shape, and longitudinal canal structure. Distinguishing features of N. promontorium are its valve shape, longitudinal canal and apex formation, and surface depression along the axial area. Neidium potapovae is distinguished by its size, formation of valve and apices and single longitudinal canal. This paper demonstrates how future phylogenetic treatments using single cell multigene sequencing can help resolve taxonomic confusion within diatoms.
从历史上看，形态物种概念在硅藻物种的界定中主观地应用了形状特征。这导致了底栖硅藻属Neidium内分类单元之间的混淆。对来自安大略省、魁北克省、新斯科舍省、纽芬兰（加拿大）和纽约（美国）的样本进行了光学显微镜（LM）和扫描电子显微镜（SEM）下的Neidium分类单元检查。傅里叶形状分析表明，形状作为一种分类特征无法区分所有物种。对样本中分离出的个体进行了三种叶绿体分子标记（rbcL、psbC和psbA）和一种核糖体分子标记（18S）的扩增和测序。使用最大似然法和贝叶斯分析，对叶绿体和18S数据集进行串联，完成了系统发育重建。串联的叶绿体数据集展示了Neidium分类单元的物种水平分辨率系统发育。18S数据集的序列分歧水平较低，无法区分Neidium分类单元。我们给出了四个先前描述物种的修订物种描述和序列数据：萨科恩Neidium、长头Neidium、化石Neidium和近缘Neidium。我们描述了三个新物种（洛氏Neidium、海角Neidium和波塔波夫Neidium），并鉴定出两种具有独特分子特征的形态。洛氏Neidium的显著特征是其大小、瓣膜形状和纵向沟结构。海角Neidium的显著特征是其瓣膜形状、纵向沟和顶端形成，以及沿轴向区域的表面凹陷。波塔波夫Neidium的特征在于其大小、瓣膜和顶端的形成以及单一纵向沟。本文展示了未来使用单细胞多基因测序的系统发育处理如何有助于解决硅藻内部的分类混乱问题。
