Darienko Tatyana, Gustavs Lydia, Pröschold Thomas
M.G. Kholodny Institute of Botany, National Academy Science of Ukraine, Kyiv, 01601, Ukraine.
Experimental Phycology and Culture Collection of Algae, University of Göttingen, D-37073, Göttingen, Germany.
J Phycol. 2016 Dec;52(6):1125-1145. doi: 10.1111/jpy.12481. Epub 2016 Nov 18.
The genera Elliptochloris and Pseudochlorella were erected for Chlorella-like green algae producing two types of autospores and cell packages, respectively. Both genera are widely distributed in different soil habitats, either as free living or as photobionts of lichens. The species of these genera are often difficult to identify because of the high phenotypic plasticity and occasional lack of characteristic features. The taxonomic and nomenclatural status of these species, therefore, remains unclear. In this study, 34 strains were investigated using an integrative approach. Phylogenetic analyses demonstrated that the isolates belong to two independent lineages of the Trebouxiophyceae (Elliptochloris and Prasiola clades) and confirmed that the genera are not closely related. The comparison of morphology, molecular phylogeny, and analyses of secondary structures of SSU and ITS rDNA sequences revealed that all of the strains belong to three genera: Elliptochloris, Pseudochlorella, and Edaphochlorella. As a consequence of the taxonomic revisions, we propose two new combinations (Elliptochloris antarctica and Pseudochlorella signiensis) and validate Elliptochloris reniformis, which is invalidly described according to the International Code for Nomenclature (ICN), by designating a holotype. To reflect the high phenotypic plasticity of P. signiensis, two new varieties were described: P. signiensis var. magna and P. signiensis var. communis. Chlorella mirabilis was not closely related to any of these genera and was, therefore, transferred to the new genus Edaphochlorella. All of the taxonomic changes were highly supported by all phylogenetic analyses and were confirmed by the ITS-2 Barcodes using the ITS-2/CBC approach.
椭圆绿藻属（Elliptochloris）和假小球藻属（Pseudochlorella）分别是为产生两种类型的似小球藻绿藻的自养孢子和细胞包而建立的。这两个属广泛分布于不同的土壤生境中，既可以自由生活，也可以作为地衣的光合生物。由于这些属的物种具有很高的表型可塑性，且偶尔缺乏特征性特征，因此往往难以鉴定。因此，这些物种的分类和命名地位仍不明确。在本研究中，采用综合方法对34个菌株进行了研究。系统发育分析表明，分离物属于绿球藻纲（Trebouxiophyceae）的两个独立谱系（椭圆绿藻属和扁藻属（Prasiola）分支），并证实这两个属关系不密切。形态学比较、分子系统发育以及小亚基核糖体DNA（SSU rDNA）和内转录间隔区（ITS）rDNA序列的二级结构分析表明，所有菌株分属于三个属：椭圆绿藻属、假小球藻属和土壤绿藻属（Edaphochlorella）。由于分类学修订，我们提出了两个新组合（南极椭圆绿藻（Elliptochloris antarctica）和显著假小球藻（Pseudochlorella signiensis）），并根据《国际藻类、真菌和植物命名法规》（ICN）指定了一个模式标本，从而使肾形椭圆绿藻（Elliptochloris reniformis）（该名称根据ICN描述无效）成为有效名称。为了反映显著假小球藻的高表型可塑性，描述了两个新变种：大型显著假小球藻（P. signiensis var. magna）和普通显著假小球藻（P. signiensis var. communis）。奇异小球藻（Chlorella mirabilis）与这些属中的任何一个都没有密切关系，因此被转移到新属土壤绿藻属。所有分类学变化均得到所有系统发育分析的高度支持，并通过ITS-2条形码（使用ITS-2/CBC方法）得到证实。
