Diversity and distribution of spine-bearing species of <i>Pinnularia</i> in eastern North America

Six species of large-celled <i>Pinnularia</i> Ehrenberg from lakes of eastern North America, <i>P. dariana</i> (A.W.F. Schmidt) Mills, <i>P. alabamae</i> Krammer, <i>P. bihastata</i> (A. Mann) R.M. Patrick, <i>P. torta</i> (A. Mann) R.M. Patrick, <i>P. rexlowei</i> sp. nov. and <i>P. spinifera</i> sp. nov. are investigated with light and scanning electron microscopy. All six species are shown to possess marginal spines, a trait sporadically encountered in <i>Pinnularia</i> and generally rare in raphid diatoms. Besides having spines, the six species differ in their frustular morphology, including appearance and position of spines. We summarize data on their ecology and distribution using a set of 702 sediment core samples from 424 lakes from eastern USA and Canada. <i>Pinnularia rexlowei</i> is only known from Quaternary lacustrine deposits in the State of Connecticut and from the surface and subfossil sediments of two lakes in northeastern USA. The other five species are relatively common, and at least one species of spine-bearing <i>Pinnularia</i> was found in 34% of studied lakes. <i>Pinnularia dariana</i> and <i>P. torta</i> reach as far north as Labrador, while <i>P. alabamae, P. bihastata</i> and <i>P. spinifera</i> were only encountered south of Canada. <i>Pinnularia alabamae</i> and <i>P. spinifera</i> are characteristic for lakes with relatively soft and slightly acidic water, while <i>P. bihastata, P. dariana</i> and <i>P. torta</i> are found in a wider range of physico-chemical conditions, including alkaline and eutrophic lakes.本研究通过光学显微镜与扫描电子显微镜，对采自北美东部湖泊的6种大型细胞羽纹藻属（Pinnularia Ehrenberg）物种展开观察分析，涉及物种包括<em>P. dariana</em> (A.W.F. 施密特) 米尔斯、<em>P. alabamae</em> 克拉默、<em>P. bihastata</em> (A. 曼恩) R.M. 帕特里克、<em>P. torta</em> (A. 曼恩) R.M. 帕特里克、<em>P. rexlowei</em> sp. nov. 以及<em>P. spinifera</em> sp. nov.。研究表明，这6个物种均具有边缘棘刺，该性状在羽纹藻属中偶有出现，而在具壳缝硅藻中则较为罕见。除棘刺特征外，6个物种在壳瓣形态上亦存在差异，具体包括棘刺的形态与着生位置。本研究依托采自美国东部与加拿大424个湖泊的702个沉积物岩芯样本，对这6个物种的生态特征与分布情况进行了汇总分析。<em>P. rexlowei</em> 仅见于美国康涅狄格州的第四纪湖相沉积，以及美国东北部两个湖泊的表层与亚化石沉积物中。其余5个物种分布相对广泛，本次研究涉及的湖泊中约34%都至少发现了一种带棘刺的羽纹藻属物种。<em>P. dariana</em>与<em>P. torta</em>的分布北界可达拉布拉多地区，而<em>P. alabamae</em>、<em>P. bihastata</em>及<em>P. spinifera</em>仅见于加拿大以南区域。<em>P. alabamae</em>与<em>P. spinifera</em>偏好水体偏软且呈弱酸性的湖泊，而<em>P. bihastata</em>、<em>P. dariana</em>及<em>P. torta</em>则可适应更广范围的理化环境，涵盖碱性与富营养化湖泊。