Abstract—

The article considers the system of the Chlorella-clade based on morphological, ecological, and molecular genetic data. Diagnostic characteristics of some genera and species are discussed, as well as the systematic position of some taxa. Molecular phylogenetic analysis of members of the Chlorella-clade showed that the use of only the 18S rRNA gene, which is considered the main phylogenetic marker for green microalgae, does not reliably distinguish species and genera within the clade. Application of more variable spacers ITS1 and ITS2 resolved the tree topology and strengthened the phylogenetic signal. The polyphyly of the genus Chlorella was confirmed. Some of the species of the genus Chlorella formed a true clade of Chlorella species, including the type species C. vulgaris, C. heliozoae, C. pituita, C. chlorelloides, C. variabilis, and Lobosphaeropsis lobophora. Other species (C. pulchelloides, C. colonials, C. rotunda, C. singularis, C. elongata, C. sorokiniana, C. lewinii, C. volutis, and C. thermophila) were found to belong to other groups, and their taxonomic affiliation requires clarification. The CBC approach and the search for compensatory mutations in conservative ITS2 regions as a tool for distinguishing species was not effective for most Chlorella-clade representatives. Efficiency of using the intron as a criterion for separating closely related species was confirmed. Analysis of genetic distances made it possible to clearly identify the strains as species of the genera Didymogenes, Hindakia, and Heynigia. Members of the Chlorella-clade are characterized by a high cryptic diversity: none of the phenotypic characteristics considered separately was sufficient for unequivocal determination of the taxonomic position of members of the clade. Some morphological features were variable, often changed or became lost after instrumental manipulations during sample preparation for the water bodies monitoring. Using a combination of morphological, biochemical, ultrastructural, physiological, ecological, and molecular genetic features (a polyphasic approach), we were able to characterize eight groups within the Chlorella-clade and to make assumptions about the division of the genera and species within these groups.

中文翻译：

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小球藻-微枝藻（Chlorophyta）的鉴定问题和隐性多样性

摘要—

本文根据形态学，生态学和分子遗传学数据考虑了小球藻的系统。讨论了某些属和物种的诊断特征，以及某些分类单元的系统位置。小球藻进化枝成员的分子系统发育分析表明，仅使用18S rRNA基因（被认为是绿色微藻的主要系统发育标记）不能可靠地区分进化枝中的物种和属。应用更多可变间隔子ITS1和ITS2可以解决树的拓扑结构并增强系统发育信号。证实了小球藻属的多重性。小球藻属的某些物种形成了真正的进化枝小球藻种类，包括普通种，普通种，Heliozoae，皮氏小球藻，小球藻，变异小球藻和球形小球藻。发现其他物种（C. pulchelloides， C。Colonials，C 。圆形大厅，C。singularis，C。elongata，C。sorokiniana，C。lewinii，C。volutis和C. thermophila）也属于其他物种，它们的物种分类学隶属关系需要澄清。CBC方法和在保守的ITS2区寻找补偿性突变作为区分物种的工具对大多数小球藻均无效阶级代表。证实了使用内含子作为分离密切相关物种的标准的效率。分析遗传距离使得可以清楚地将菌株鉴定为Didymogenes，Hindakia和Heynigia属。小球藻的成员进化枝的特征是高度隐秘的多样性：单独考虑的表型特征不足以明确确定进化枝成员的分类位置。在用于水体监测的样品制备过程中，通过仪器操作后，某些形态特征是可变的，经常变化或丢失。结合形态学，生化，超微结构，生理学，生态学和分子遗传学特征（多相方法），我们能够表征小球藻内的八个基团，并对这些基团的属和种进行划分组。