Desmids (Zygnematophyceae) from the littoral zone of an urban artificial lake: taxonomic aspects and geographical distribution

Abstract Aim: The aim of this study was to assess the taxonomic aspects and geographical distribution of the periphytic desmids from two different substrates in the littoral zone of an urban artificial lake. Methods Samples of epiphytic and epilithic desmids were collected by grass and rock scraping, respectively, in two stations in the Cascavel municipal lake, Paraná, during April 2015, and March 2016 and 2017. In the laboratory, the taxa obtained from the samples were photographed and their morphometric characteristics recorded. The species composition of the desmid was characterized, and the frequency of occurrence as well as the geographic distribution of each taxon in the Paraná State were recorded. Results We identified 35 taxa, distributed in 10 genera. The most representative were Closterium Nitzsch ex Ralfs and Cosmarium Corda ex Ralfs. A high occurrence of sporadic taxa (60%) was observed and among the recorded taxa, the most frequent were Cosmarium pseudoconnatum Nordstedt var. pseudoconnatum and Desmidium grevillei (Kützing ex Ralfs) De Bary. Nine taxa were exclusive to the epilithic substrate and only Netrium digitus (Ralfs) Itzigsohn & Rothe var. digitus was exclusive to the epiphytic substrate, while the remaining 25 taxa occurred in both substrates. Seven taxa are new records for the Paraná State. Conclusion Although our results are of qualitative nature, they provide baseline data on the biogeographic distribution of taxa, which are crucial for future taxonomic and ecological studies that might contribute to the preservation of the biodiversity.

研究目的：本研究旨在评估巴拉那州卡斯卡韦尔市立湖湖滨带两种不同基质上附生鼓藻（periphytic desmids）的分类学特征与地理分布。
方法：2015年4月、2016年3月及2017年3月，于该湖的两个采样站点，分别通过刮取水草与岩石的方式采集附生（epiphytic）及石生（epilithic）鼓藻样本。实验室中，对样本中获取的分类单元进行拍照并记录其形态计量特征；随后解析鼓藻的物种组成，同时记录各分类单元的发生频率及其在巴拉那州的地理分布。
结果：本研究共鉴定出35个分类单元，隶属于10个属。其中占比最高的类群为梭鼓藻属（Closterium Nitzsch ex Ralfs）与角星鼓藻属（Cosmarium Corda ex Ralfs）。观测到60%的类群为偶见类群，在已记录的类群中，发生频率最高的为假连接角星鼓藻（Cosmarium pseudoconnatum Nordstedt var. pseudoconnatum）与格雷维尔连合鼓藻（Desmidium grevillei (Kützing ex Ralfs) De Bary）。9个分类单元仅分布于石生基质，仅指状鼓藻（Netrium digitus (Ralfs) Itzigsohn & Rothe var. digitus）仅见于附生基质，剩余25个分类单元在两种基质上均有发现。另有7个分类单元为巴拉那州的新记录类群。
结论：尽管本研究结果属于定性研究范畴，但仍提供了相关类群生物地理分布的基础数据，此类数据对于未来开展分类学与生态学研究、助力生物多样性保护工作具有关键参考价值。