Morphology and phylogenetic relationships of the CW group of the unicellnlar green algae

在对基体顺时针排列的陆生单细胞绿藻的分子系统发育研究中，发现它们属于一个单系群(CW群)。在分子系统发育的基础上，对在分类中被认为重要的形态特征进行了评价。营养细胞的四分体和类肉质结构曾被认为是绿腐目的特征，它们出现在不同的分支中，从而支持了这些特征不能用于在目的分类的观点。随着年龄的增长，营养细胞发育的多核条件在CW组内的不同亚类中进化。在不同的分支中发现了一种小行星叶绿体，并指出，由于这种类型的叶绿体经常与轴…混淆，因此在鉴定时应注意形态观察。更多的是顶层的。在一个分支中发现了网状或海绵状的叶绿体，其中包括突变体和单核生物，导致这些叶绿体类型以联会的形式出现。游动孢子的形态特征，如细胞体周围有无细胞壁，以及细胞壁层的组成，在一些亚纲中是联会的。鞭毛长度、鞭毛方向和鞭毛器的组成也是几个指定亚纲共有的特征。虾青素的积累以联体的形式出现在两个分支中，其中一个亚分支包括具有运动和非运动营养细胞的生物体。在土壤环境以外的生境中，海水生物被置于单系分支，表明它们是由生活在淡水区的生物次生发展而来的。在淡水环境中固定在底物上的单细胞绿藻被发现在几个不同的系统发育谱系中进化。三硫浮萍叶片内的共生藻类被置于一个由营养细胞和游动孢子的形态与该共生体相似的有机体组成的分支中。较少

In the molecular phylogenetic investigation on the terrestrial, unicellular green algae having basal bodies arranged in clockwise orientation, which have been classified in the four orders, it was found that they were included in a monophyletic group (CW group). The morphological characters which have been assumed to be important in classification were evaluated on the basis of the present molecular phylogeny. The tetrad and sarcinoid formations of vegetative cells, which were once considered as features of the order Chlorosarcinales appeared in different clades, and thus, the opinion that these features could not be used for classification at the order rank was supported. Multinucleate conditions of vegetative cells developing with age evolved in different subclades within the CW group. An asteroid chloroplast was found in different clades, and it was pointed that morphological observation for identifying should be careful, because this type of chloroplast is often confused with axile … More and parietal ones. A net-like or sponge-like chloroplast was found in a clade, in which both mutinuleate and uninucleate organisms were included in it's subclades, resulting that these chloroplast types occurred as synapomorphy. The morphological features of zoospores, such as presence or absence of cell wall around cell body, and composition of cell wall layers, were synapomorphy in some subclades. The flagellar lengths, direction of flagella, and compositions of flagellar apparatus were also characters shared in several specified subclades. Accumulation of astaxanthin appeared in two clades as synapomorphy, and organisms having motile and non-motile vegetative cells were included in one of these subclades. In habitats other than soil environment, sea water inhabitants were placed in a monophyletic branch, showing that they secondarily developed from an organism lived in freshwater regions. Unicellular green algae fixing on substrates in freshwater environment were found to evolved in several different phylogenetic lineages. A symbiotic alga within leaves of Lemna trisulca was placed in a branch comprising organisms having similar morphology of vegetative cells and zoospores to this symbiont. Less