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Stigeoclonium is a genus of green algae that is widely distributed in freshwater habitats around the world. The genus comprises species with variously developed prostrates and erect systems of uniseriate branched filaments and grows attached to a wide range of different surfaces. It holds significant promise for applications in water quality indicators, sewage treatment, and the development of high-value-added products. Nevertheless, our comprehension of Stigeoclonium remains unclear and perplexing, particularly regarding its fundamental systematic taxonomy. Recent molecular analyses have revealed that the morphologically well-defined genus Stigeoclonium is polyphyletic and requires taxonomic revision. Phylogenetic analysis based on a single molecular marker and limited samples is insufficient to address the polyphyletic nature of Stigeoclonium. In the present study, 34 out of 45 strains of Stigeoclonium were newly acquired from China. Alongside the morphological data, a concatenated dataset of three markers (18S rDNA + ITS2 + tufA) was utilized to determine their molecular phylogeny. The phylogenetic analysis successfully resolved the broadly defined Stigeoclonium into three robustly supported clades (Stigeoclonim tenue clade, S. farctum clade, and S. helveticum clade). The morphological characteristics assessment results showed that the cell type of the main axis-producing branch, considered a crucial morphological characteristic of the Stigeoclonium taxonomy, did not accurately reflect the real phylogeny of the genus. A new taxonomical classification of the genus Stigeoclonium was proposed based on zoospores' germination types, which aligned well with the phylogenetic topologies. Species where zoospores showed erect germination (S. helveticum clade) formed a distinct monophyletic clade, clearly separated from the other two clades, with zoospores showing prostrate germination or pseudo-erect germination. Consequently, a new genus, Pseudostigeoclonium gen. nov., is suggested to include all species in the broadly defined Stigeoclonium with zoospores with erect germination. The taxonomic diversity is supported by distinctive morphological differences and phylogenetic divergence within the broadly defined Stigeoclonium identified in this study. Further evaluation of the genus Stigeoclonium is necessary, especially via examining additional specimens and re-evaluating morphological characters under precisely defined laboratory conditions. [ABSTRACT FROM AUTHOR]

The green algal genus Aphanochaete consists of species with uniseriate, simple, or irregularly branched, prostrate, and erect filaments, with cells bearing unsheathed unicellular hairs with or without bulbous bases. In this study, 12 strains of Aphanochaete were isolated and successfully cultured and their phylogenetic relationships were determined using the morphological data, along with 18 S rDNA and a concatenated dataset of four markers (18 S + 5.8 S + ITS2 + partial 28 S rDNA). Within the genus Aphanochaete, three types of zoospore germination and two types of unicellular hairs distinguished all the clades of this genus, which was consistent with molecular phylogeny and the compensatory case changes in ITS2 secondary structures. Aphanochaete xiantaoensis was determined to be a new species owing to its unique unipolar zoospore germination, which clearly differed from bipolar or cruciate zoospore germination in other species. While molecular phylogeny indicated that the number of hairs per cell was the poor taxonomic characteristics, we propose to list A. polychaete as a synonym of A. repens. Phylogenetic analyses revealed that different species within the genus Aphanochaete might have evolved from bipolar zoospore germination toward cruciate and unipolar zoospore germination. [ABSTRACT FROM AUTHOR]

Chaetophora lobata is the type species of the polyphyletic genus Chaetophora. Clarification of its species identification, phylogenetic relationships, and plastome characteristics is helpful for taxonomic revisions and evolutionary studies of this genus. This study presents detailed information on morphology, culture, phylogenetic analysis, phylogenomics and comparative genomics of C. lobata. The complete morphological description and phylogenetic analyses based on nuclear rDNA and chloroplast protein-coding genes were robust for the identification of C. lobata. Moreover, de novo sequencing was used to determine the 222 213 bp chloroplast genome, which lacked inverted repeats as in all other members of the Chaetophorales. The chloroplast DNA (cpDNA) of C. lobata was found to be AT-rich (68.2%), consisting of 67 protein-coding genes, among which 62 genes were encoded on the plus strand and five genes were encoded on the minus strand with significant imbalance in distribution. Additionally, 28 tRNA genes, three rRNA genes, 16 introns and 18 putative open reading frames (ORFs) were annotated. Eight ORFs arranged in a row occupied about 18 kbp between psaA and atpI genes, and 16 introns (14 group I introns and 2 group II introns) were annotated in nine genes. Six genes contained nine intronic ORFs. Synteny and rearrangements analysis clearly showed the closest relationships between Chaetophora sp. and C. lobata. Substitution rate estimation indicated that the cpDNA of Chaetophorales was under purifying selection and most species were under similar evolutionary pressure. These findings can help advance research on the taxonomy and phylogeny of the order Chaetophorales. [ABSTRACT FROM AUTHOR]

Cephaleuros is a subaerial green alga widely distributed in tropical and subtropical regions. In this study, we investigated the taxonomy of Cephaleuros in southern China. Eight morphospecies (C. virescens, C. karstenii, C. expansus, C. drouetii, C. diffusus, C. tumidae-setae, C. lagerheimii and C. parasiticus) were identified according to previous descriptions, among which C. karstenii was the most frequently recorded. Subsequently, molecular phylogeny of Cephaleuros was inferred from 18S rDNA, ITS rDNA, 28S rDNA and rbcL sequences. Cephaleuros was subdivided into nine clades based on ITS analysis, which were recovered in phylogenies of two concatenated datasets (18S+ITS+28S and 18S+ITS+28S+rbcL). Molecular analyses revealed that Cephaleuros was composed of two main lineages, with one lineage comprising mostly samples of C. karstenii and C. virescens and the other comprising other species. The molecular phylogenies were not congruent with conventional morphological classifications, although some clades were distinguished by one or more diagnostic features. While the morphological features used to distinguish Cephaleuros spp were not reliable, the rbcL gene proved to be a good marker for identification of Cephaleuros. The ITS2 secondary structure prediction model showed that Cephaleuros spp have one ring structure with four helices, with Helix III being the longest without a branch in clades 3, 5 and 8. The present study represents the most detailed taxonomic assessment of Cephaleuros available to date. Further taxonomic research incorporating samples from the type locality is necessary for the reassessment of C. virescens. [ABSTRACT FROM AUTHOR]

The green algal genus Oncosaccus, endemic to China, has previously been classified in Chlamydomondales (Chlorophyceae). In the present study, two green algal specimens from west China were identified as Oncosaccus tetrasporoides due to their unique colonial form with numerous cells embedded in a thick gelatinous envelope without perforations and pseudocilia. Molecular data from two nuclear loci (18S rDNA and ITS) were used to test the hypothesised membership of this taxon. The molecular data clearly showed that Oncosaccus did not have close affinities to the Chlamydomondales, but instead belonged to the order Chaetopeltidales in the family Chaetopeltidaceae, and had a close relationship with Chaetopeltis and Pseudulvella. The ultrastructure of Oncosaccus tetrasporoides resembled Chaetopeltis and Pseudulvella, and adjacent cells lacked plasmodesmata, and the pyrenoid matrix was traversed by a cytoplasmic channel instead of the thylakoid membrane were present. This morphology supported the molecular data and confirmed this group's placement in the Chaetopeltidales. The present study expanded our understanding of the morphological features of green algae, particularly those of the poorly studied Chaetopeltidales. Nonetheless, a phylogenetic re-evaluation based on large samples in conjunction with molecular analyses is needed. [ABSTRACT FROM AUTHOR]

The genus Hariotina was established in 1889 based on the type species Hariotina reticulata. This species was then transferred to Coelastrum by Senn (1899). The genus Hariotina was eventually restored by Hegewald et al. (2002) based on morphological characteristics. Species of Hariotina are ubiquitous in fresh water, especially in some tropical and subtropical areas. The taxonomic position of the genus is now considered to be within the family Scenedesmaceae. However, until now, there was an insufficient understanding of the molecular diversity within this genus, and the related reference sequences in the database were inadequate to resolve the species taxonomy. In this study, 20 strains of Hariotina were identified and successfully cultured in the laboratory. We used a combined approach, joining molecular and morphological analyses, to determine their taxonomic relationships and phylogenetic positions. The molecular analyses based on 18S rDNA+ITS sequences and the tufA gene resolved the analysed strains into at least six species, including the known species H. reticulata and H. polychorda and four new species herein described, i.e. H. hainanensis sp. nov., H. compacta sp. nov., H. guilinensis sp. nov. and H. laxa sp. nov. The genus Hariotina was confirmed in the Scenedesmaceae as a monophyletic clade that was closely related to the genus Coelastrum in tufA gene phylogeny. Strains with H. reticulata morphotype were found to be located on two different branches, and formed sister relationships with the other two morphologically distinct species. In addition, the topology was supported by all three DNA markers. The congruence between the phylogeny and the classical taxonomic system based on morphological criteria for this taxon is discussed. [ABSTRACT FROM AUTHOR]

The genus Coelastrella was established by Chodat (Bull. Soc. Bot. Geneve, 13 [1922] 66), and was characterized as being unicellular or in few‐celled aggregations with many longitudinal ribs on the cell wall. Many species of this genus showed strong ability to accumulate carotenoids and oils, so they have recently attracted much attention from researchers due to its potential applicability in the energy and food industries. In this study, a total of 23 strains of Coelastrella were sampled from China, and three new species and two new varieties were described: C. thermophila sp. nov., C. yingshanensis sp. nov., C. tenuitheca sp. nov., C. thermophila var. globulina var. nov., C. rubescens var. oocystiformis var. nov. Besides 18S rDNA and ITS2 sequences, we have newly sequenced the tufA gene marker for this taxon. Phylogenetic analysis combined with morphological studies revealed four morphotypes within the Coelastrella sensu lato clade, which contained the morphotype of original Coelastrella, original Scotiellopsis, Asterarcys, and morphotype of C. vacuolata and C. tenuitheca sp. nov. The relationships between morphological differences and phylogenic diversity based on different markers were discussed. Our results support that 18S rDNA was too conserved to be used a species‐specific or even a genus‐specific marker in this clade. The topology of tufA gene‐based phylogenetic tree had a better match with the morphological findings. [ABSTRACT FROM AUTHOR]

Abstract: The Parachlorella clade was put forward as a group within the family Chlorellaceae in 2004. Recent molecular analyses have revealed that Dictyosphaerium morphotype algae form several independent lineages within the Parachlorella clade, and new genera and species have been established. In this study, we focus on the diversity of Dictyosphaerium morphotype algae within the Parachlorella clade, based on 42 strains from China. We used combined analyses of morphology and molecular data based on SSU and internal transcribed spacer region (ITS) rDNA sequences to characterize these algae. In addition, the secondary structure of ITS2 was compared to delineate new lineages. Our results revealed high phylogenic diversity of Dictyosphaerium morphotype algae, and we describe five distinct lineages. We examined the morphological features of these five lineages, and morphological differences are difficult to find compared with other Dictyosphaerium morphotype algae. The five distinct lineages were not described as new genera currently. We lastly discuss the taxonomic problems regarding the Dictyosphaerium morphotype within the Parachlorella clade, and possible solutions are considered. [ABSTRACT FROM AUTHOR]

The order Trentepohliales is composed of a complex of five aerial genera of branched filamentous green algae,Trentepohlia, Printzina, Phycopeltis,CephaleurosandStomatochroon; polyphyly has been discovered in some of these genera and species. To clarify the diversity and some taxonomic problems in the Trentepohliales, we collected specimens from southern China and successfully cultured the majority of them. We carefully observed morphological traits and performed phylogenetic analyses based on new 18S and ITS rDNA sequences obtained during the present study. Our results suggested that the ostiole position of the zoosporangia might effectively indicate the main lineages of Trentepohliales, with reassessment of the generaTrentepohliaandPrintzinarequired based on this ostiole positioning. However, further molecular investigation, particularly for the genusPhycopeltis, is required. Phenotypic plasticity was very common inTrentepohliaandCephaleurosand the traditionally circumscribed taxa may not be reliable. InCephaleuros, the lichenized species do not form a single clade and most species are paraphyletic. Additionally, we suggest that a lack of description of the internal systems could be one reason for the difficulties in species identification. Further taxonomic studies should focus on an emendation ofCephaleurosand elucidating the molecular diversity ofPhycopeltis. [ABSTRACT FROM AUTHOR]

Abstract: In 2008–2010, several freshwater dinoflagellate blooms caused by Peridiniopsis spp. were observed in China. P. penardii and P. niei sampled from various geographical localities were examined by means of light and scanning electron microscopy. After comparing morphological and molecular differences, the new freshwater variety Peridiniopsis penardii var. robusta var. nov. (Peridiniales, Dinophyceae) found in Manwan Reservoir, Yunnan Province was described. The new variety differed from P. penardii since it possessed numerous robust antapical spines and a conspicuous apical spine. Molecular phylogenetic analyses based on SSU, LSU and ITS indicated P. niei, P. penardii and P. penardii var. robusta were closely related with P. kevei, and clustered into a monophyletic clade. The new variety possessed an endosymbiotic diatom which was similar to P. penardii and P. kevei, whereas the endosymbiont was not present in cells of P. niei. The endosymbiont SSU and ITS phylogenies showed that the endosymbionts of these three dinoflagellates were closely related to members of Thalassiosirales. Furthermore it was concluded that the endosymbionts might originate from Discostella-like species. [Copyright &y& Elsevier]