Taxonomic revision and species delimitation of coccoid green algae currently assigned to the genus Dictyochloropsis (Trebouxiophyceae, Chlorophyta)
Taxonomic revision and species delimitation of coccoid green algae currently assigned to the genus Dictyochloropsis (Trebouxiophyceae, Chlorophyta)
复制标题
DOI：
10.1111/jpy.12422
复制
发表时间：
2016-08
影响因子：
2.9
通讯作者：
P. Škaloud;T. Friedl;C. Hallmann;A. Beck;Francesco Dal Grande
中科院分区：
文献类型：
--
作者：
P. Škaloud;T. Friedl;C. Hallmann;A. Beck;Francesco Dal Grande
球形绿色藻类传统上分类在网绿球藻中，成熟时具有复杂的网状叶绿体，没有核蛋白。它们作为自由生活的生物体或与地衣形成真菌相关联占据了非常多样化的生态位，最近被证明在Trebouxiophyceae内形成了两个不同的谱系。我们使用多相的方法来修订该属的分类。基于18 S rRNA基因的系统发育分析，以及使用比较常规的光学和共聚焦显微镜进行的详细形态学调查，我们将这些谱系分配给两个属，Dictyochloropsis和Symbiochloris gen. nov。网绿球藻仅包括具有网状叶绿体的自由生活的藻类，在某些个体发育阶段形成平行排列的裂片，并且仅通过自生孢子繁殖。这与Geitler最初对Dictyochloropsis的诊断一致，但与Tschermak-Woess后来的修正不一致。因此，Dictyochloropsis sensu Tschermak-Woess的物种被分配给Symbiochloris，并提出了新的组合。共生绿球藻属包括具有叶状叶绿体的自由生活和/或地衣化的藻类，并且通过形成游动孢子进行繁殖，游动孢子的特征在于两个近顶端的等鞭毛体在扁平的顶端附近对称地出现。此外，使用基于合并的方法，ITS转录本的形态特征和二级结构，我们推断了新提出的属内的种边界和分类关系。共鉴定出网绿球藻属2种和共生绿球藻属9种，其中包括新记录种D. asterochloroides，S. handae，S. tropica和S.切马基亚科。我们的研究结果进一步支持了Trebouxiophyceae内自孢子菌类群的非单系性。
Coccoid green algae traditionally classified in Dictyochloropsis have a complex, reticulate chloroplast, when mature, without a pyrenoid. They occupy remarkably diverse ecological niches as free‐living organisms or in association with lichen‐forming fungi and were recently shown to form two distinct lineages within Trebouxiophyceae. We used a polyphasic approach to revise the taxonomy of the genus. Based on phylogenetic analysis of the 18S rRNA gene, and detailed morphological investigation using comparative conventional light and confocal microscopy, we have assigned these lineages to two genera, Dictyochloropsis and Symbiochloris gen. nov. We have reconsidered the diagnostic generic features as follows: Dictyochloropsis comprises only free‐living algae with a reticulate chloroplast, forming lobes in a parallel arrangement at some ontogenetic stages, and which reproduce only by means of autospores. This agrees with Geitler's original diagnosis of Dictyochloropsis, but not with the later emendation by Tschermak‐Woess. Consequently, the species of Dictyochloropsis sensu Tschermak‐Woess are assigned to Symbiochloris, with new combinations proposed. Symbiochloris encompasses free‐living and/or lichenized algae with lobed chloroplasts and that reproduce by forming zoospores characterized by two subapical isokont flagella that emerge symmetrically near the flattened apex. In addition, using coalescent‐based approaches, morphological characters and secondary structure of ITS transcripts, we inferred species boundaries and taxonomic relationships within the newly proposed genera. Two species of Dictyochloropsis and nine species of Symbiochloris are delimited, including the newly described species D. asterochloroides, S. handae, S. tropica, and S. tschermakiae. Our results further support the non‐monophyly of autosporine taxa within Trebouxiophyceae.