ABSTRACT Filamentous conjugating green microalgae (Zygnematophyceae, Streptophyta) belong to the most common primary producers in polar hydro-terrestrial environments such as meltwater streamlets and shallow pools. The mats formed by these organisms are mostly composed of sterile filaments with Zygnema morphology, but the extent of their diversity remains unknown. Traditional taxonomy of this group is based on reproductive morphology, but sexual reproduction (conjugation and formation of resistant zygospores) is very rare in extreme conditions. In the present study we gave the first record of zygospore formation in Svalbard field samples, and identified conjugating filaments as Zygnemopsis lamellata and Zygnema cf. calosporum. We applied molecular phylogeny to study genetic diversity of sterile Zygnema filaments from Svalbard in the High Arctic. Based on analysis of 143 rbcL sequences, we revealed a surprisingly high molecular diversity: 12 Arctic Zygnema genotypes and one Zygnemopsis genotype were found. In addition, we characterized individual Arctic genotypes based on cell width and chloroplast morphology using light and confocal laser scanning microscopy. Our findings highlight the importance of a molecular approach when working with sterile filamentous Zygnematophyceae, as hidden diversity might be very beneficial for adaptation to harsh environmental conditions, and experimental results could be misinterpreted when hidden diversity is neglected.

中文翻译：

---

来自斯瓦尔巴群岛（高北极）的 Zygnema 和 Zygnemopsis（Zygnematophyceae，Streptophyta）的分子和形态多样性

摘要 丝状共轭绿色微藻（Zygnematophyceae，Streptophyta）属于极地水文环境中最常见的初级生产者，如融水小溪和浅水池。这些生物形成的垫子主要由具有 Zygnema 形态的无菌细丝组成，但其多样性的程度仍然未知。该群体的传统分类学基于生殖形态，但在极端条件下，有性生殖（抗性接合孢子的结合和形成）非常罕见。在本研究中，我们首次记录了斯瓦尔巴群岛田间样品中接合孢子的形成，并将接合丝鉴定为 Zygnemopsis lamellata 和 Zygnema cf。孢子菌。我们应用分子系统发育来研究来自高北极斯瓦尔巴群岛的不育 Zygnema 细丝的遗传多样性。基于对 143 个 rbcL 序列的分析，我们揭示了令人惊讶的高分子多样性：发现了 12 个北极 Zygnema 基因型和一个 Zygnemopsis 基因型。此外，我们使用光和共聚焦激光扫描显微镜根据细胞宽度和叶绿体形态对个体北极基因型进行了表征。我们的研究结果强调了分子方法在处理不育丝状 Zygnematophyceae 时的重要性，因为隐藏的多样性可能非常有利于适应恶劣的环境条件，而当隐藏的多样性被忽视时，实验结果可能会被误解。我们使用光和共聚焦激光扫描显微镜根据细胞宽度和叶绿体形态表征了个体北极基因型。我们的研究结果强调了分子方法在处理不育丝状 Zygnematophyceae 时的重要性，因为隐藏的多样性可能非常有利于适应恶劣的环境条件，而当隐藏的多样性被忽视时，实验结果可能会被误解。我们使用光和共聚焦激光扫描显微镜根据细胞宽度和叶绿体形态表征了个体北极基因型。我们的研究结果强调了分子方法在处理不育丝状 Zygnematophyceae 时的重要性，因为隐藏的多样性可能非常有利于适应恶劣的环境条件，而当隐藏的多样性被忽视时，实验结果可能会被误解。