Toward a monograph of non-marine Ulvophyceae using an integrative approach (Molecular phylogeny and systematics of terrestrial Ulvophyceae II.)

Phylogenetic analyses of SSU rDNA sequences have shown that coccoid and filamentous green algae are distributed among all classes of the Chlorophyta. One of these classes, the Ulvophyceae, mostly contains marine seaweeds and microalgae. However, new studies have shown that there are filamentous and sarcinoid freshwater and terrestrial species (including symbionts in lichens) among the Ulvophyceae, but very little is known about these species. Ultrastructural studies of some of them have confirmed that the flagellar apparatus of zoospores (counterclockwise basal body orientation) is typical for the Ulvophyceae. In addition to ultrastructural features, the presence of a “ Codiolum ”-stage is characteristic of some members of this algal class. We studied more than 50 strains of freshwater and terrestrial ulvophycean microalgae obtained from the different public culture collection and our own isolates using an integrative approach. Three independent lineages of the Ulvophyceae containing terrestrial species were revealed by these methods. Unexpectedly each of these lineages contained several isolates that morphologically developed a high degree of phenotypic plasticity, and included hidden phylogenetic diversity that let us to the description of several new genera and species.


Introduction
Traditionally, most freshwater and terrestrial green algae belonged to the classes Chlorophyceae and Trebouxiophyceae (Ettl & Gärtner 1995). In contrast the class Ulvophyceae is dominated by species that are distributed in marine habitats. Phylogenetic analyses of terrestrial green algae using SSU rDNA sequences have shown that many filamentous and sarcinoid algae that were previously assigned to the Chlorophyceae are members of the Ulvophyceae. For examples, the genera Dilabifilum (Thüs et al. 2011), Planophila, Pseudendocloniopsis (Friedl & O'Kelly 2002), Pseudendoclonium, Ulothrix zonata, Gloeotilopsis (Friedl 1996), Desmochloris (Darienko et al. 2009, Watanabe et al. 2001, Hazenia (Skaloud et al. 2013a), Helicodictyon (Watanabe et al. 2001, Watanabe 2002, and Ignatius (Watanabe & Nakayama 2007) are ulvophytes isolated from terrestrial or freshwater habitats. However, the species concepts within these genera remain unresolved because of the phenotypic plasticity as demonstrated for Desmochloris mollenhaueri Darienko, Friedl et Pröschold (Darienko et al. 2009). Many ulvophycean taxa have been described but never investigated using modern molecular techniques (e.g. Borzi 1883, Nichols & Bold 1965, Biebel 1968, Tupa 1974. Using an integrative approach in the first study of 'Molecular phylogeny and systematics of terrestrial Ulvophyceae', the species of the genus Desmochloris could be differentiated based on morphology, phylogeny, and molecular signatures using the secondary structures of ITS-1 and ITS-2. Originally the type species of Desmochloris, D. halophila (Guillard, Bold et MacEntree) Watanabe, Kuroda et Maiwa, was described as Chlorosarcinopsis, a genus belonging to the Chlorophyceae, which is common in terrestrial habitats (Guillard et al. 1975). As shown for D. mollenhaueri, terrestrial ulvophytes change morphology depending on different salinities (Darienko et al. 2009), resulting in their difficult identification using traditional keys. To resolve this problem, robust molecular phylogenetic reconstruction and DNA barcoding can help to identify the microorganisms at generic and species levels and reveal hidden diversities among the Ulvophyceae.
The aim of the second contribution is to resolve the taxonomic status and phylogenetic position of the genera abovementioned. Despite the different generic assignment of those taxa, most species have a similar morphology (cell packages with a tendency to form branched pseudofilaments or filaments) and show a high phenotypic plasticity, making it very difficult to identify them at the species level. Some of these taxa were originally described as members of the genera Pseudendoclonium Wille, Pseudopleurococcus Snow emend. Vischer, or Dilabifilum Tschermak-Woess, which are similar in morphology but are separated from each other by the absence of certain morphological features. For example, the first two genera differ only by the absence of zoospores and the exclusive occurrence in terrestrial habitats by Pseudopleurococcus. Dilabifilum was separated by the formation of Microthamnion-like branching filaments, which do not appear in Pseudendoclonium. Considering the evaluation of these features, several authors considered these characters differently, resulting in different generic assignments of these species (see, e.g., Printz 1964, Bourrelly 1966, 1990, Ettl & Gärtner 1995. Other genera were described exclusively based on ecological preferences. For example, Geitler (1942) described the genus Rhexinema solely based on its growth in neuston.
To solve these taxonomic problems, we used the integrative approach introduced by Pröschold & Leilaert (2007) to the abovementioned genera. The detailed procedure has been described by Darienko et al. (2016), and it is based on phylogenetic analyses of SSU and ITS rDNA sequences in combination with the morphology and life cycle of the investigated strains. According to the phylogeny of SSU rDNA sequences, terrestrial and freshwater ulvophytes belong to five independent lineages called Chlorocystis-, Pirula-, Trichosarcina-, Ignatius-, and Trentepohlia-clades sensu Pröschold & Leliaert (2007). The taxonomic status of some genera and their abovementioned species must be resolved and is the topic of this contribution. As many publications have shown, the phylogeny of green algae can be clearly resolved using a concatenated data set of SSU and ITS rDNA sequences. Among monophyletic lineages (= genera), the species concept is based on the ITS-2/CBC approach described by Demchenko et al. (2012) and Darienko et al (2015Darienko et al ( , 2016. In this approach, the internal transcribed spacer region 2 (ITS-2) has been used to delimitate organisms at the species level. Coleman (2000) has shown that strains of the volvocalean green algae (Chlorophyceae), which are able to mate representing a Z(ygote)-clade or biological species, have identical conserved regions of ITS-2. In contrast, if two species differ in at least one compensatory base change (CBC; i.e., A-U to G-C), they cannot mate. Therefore, ITS-2 can be used for species delimitation and has been used in many studies of the green algae.
The aims of this study are as follows: (1) to provide a robust phylogeny of non-marine ulvophytes, which will then be the basis of (2) species delimitation among the abovementioned genera; (3) to distinguish the species by application of the ITS-2/CBC approach; (4) to identify necessary taxonomic changes, including descriptions of new genera and species; (5) to generalize the applied approach to identify the hidden diversity among this morphologically variable group of green algae.

Algal material and culture conditions
In this study, more than 50 strains with different affiliations were obtained from public and working culture collections. Detailed information about their habitat and origin is presented in Table S1. All of the algal strains were cultivated in modified Bold ìs Basal Medium (3N-BBM+V; medium 26a in Schlösser 1997), Basal and Desmidiacean medium (ES, MiEB12; media 1 and 7 in Schlösser 1994) and in media with different salinities (SWES, and 1/2SWES; media 5, 6 in Schlösser 1994, respectively) under standard conditions (light:dark cycle of 14:10 hrs at 18°C and 50 μmol photons/m 2 s 1 provided by daylight fluorescent tubes, Osram L36W/954 Lumilux de lux daylight, Munich, Germany). For species identification, the identification keys of Ettl & Gärtner (1995, Printz (1964), Tupa (1974), and Starmach (1972) were used and the morphology of the strains was compared with the original species descriptions. For the light microscope investigations, an Olympus BX-60 microscope was used (Olympus, Tokyo, Japan), and the micrographs were obtained with a ProgRes C14 plus camera using the ProgRes Capture Pro imaging system (version 2.9.0.1; both from Jenoptik, Jena, Germany).

ITS-2 secondary structures and ITS-2/CBC approach
For phylogenetic analyses and comparisons of ITS-2 sequences it is crucial to obtain an accurate model of the secondary structure. The commonly used computer programs (mfold; Zuker 2003 and RNAfold;Lorenz et al. 2011) use the thermodynamical model (minimal energy) to fold RNA sequences. CONTRAfold (Do et al. 2006), another program used a stochastic approach for the RNA folding. Both methods require complete and unambiguous ITS-2 sequences with their flanking regions of the 5.8S and LSU sequences. For accurate analyses described in the following chapters we used all sequences of the datasets analyzed for Figs 2 and 3 and compared them with those already published to prove if ITS-2 is suitable as phylogenetic marker and as barcode marker. Those sequences have been folded using the three programs mentioned above with the three constraints described as follows: (1) the last 25 bases of the 5.8S rRNA and the first 25 of the LSU rRNA must bind and form the 5.8S/LSU stem, (2) the pyrimidine/pyrimidine mismatch (the first RNA processing site) in Helix II after the 5-7th base pair has to be present in the structure, and (3) the second RNA processing site, the GGU motif characteristic for green algae, has to be at the 5' site in Helix III (for details about the processing sites and constraints; see Coleman 2003, Cote et al. 2002. The ITS-2 secondary structures of each type species were visualized using the program VARNA (Darty et al. 2009) and presented in the supplemental material (Figs S2).
For the usage of ITS-2 as DNA Barcode it is absolutely necessary to obtain ITS sequences free of ambiguities with the flanking regions of 5.8S and LSU rDNA to avoid analyzing pseudogenes. Only then it is possible to fold a unique secondary structure model of ITS-2 with the constraints mentioned above. For species identification among the genera, the ITS-2/CBC approach was applied following exactly the procedure that is described in Darienko et al. (2015) for Coccomyxa. FIGURE 1. Molecular phylogeny of the Ulvophyceae based on SSU rDNA sequence comparisons. The phylogenetic tree shown was inferred using the maximum likelihood method based on a data set of 1770 aligned positions of 106 taxa using PAUP 4.0b10. For the analysis, the GTR+I+G (base frequencies: A 0.23760, C 0.22733, G 0.28379, T 0.25128; rate matrix A-C 1.0063, A-G 2.3095, A-T 1.3005, C-G 0.7427, C-T 4.0954, G-T 1.0000) with the proportion of invariable sites (I = 0.5552) and gamma shape parameter (G = 0.4527) was chosen, which was calculated as the best model by Modeltest 3.7. The branches in bold are highly supported in all analyses (Bayesian values > 0.95 calculated with PHASE and MrBayes; bootstrap values > 70% calculated with PAUP using maximum likelihood, neighbor-joining, maximum parsimony and RAxML using maximum likelihood). The sister group of the Oltmannsiellopsis-clade was chosen as outgroup. The clade designations was given after the represented genera. The strains originally assigned as Dilabifilum and Pseudendoclonium basiliense are marked with * and # behind the accession number, respectively. The generic names after taxonomic revision are given in white boxes.
Considering this approach, we extracted the conserved region of ITS-2 from each of 54 strains as follows: (1) 16 base pairs of the 5.8S/LSU stem, (2) three basal base pairs of Helix I, (3) eleven base pairs of Helix II including the pyrimidine-pyrimidine mismatch, and (4) all base pairs of Helix III. The resulting data set was then aligned manually. These alignments have been translated into base pair alignment by usage of a number code for each base pair (1 = A-U; 2 = U-A; 3 = G-C; 4 = C-G; 5 = G•U; 6 = U•G). The resulting number code of each strain is given in Figs S2. These barcodes of each genus were compared to detect compensatory base changes (CBCs), hemi-CBCs (HCBCs) and/or insertion/deletion, single or unpaired bases. The results are summarized in Table 1 and Figs S2.

Phylogenetic distribution of non-marine Ulvophyceae
Phylogenetic analyses of the SSU rDNA sequences clearly revealed that all non-marine ulvophytes were distributed into two major lineages within the Ulvophyceae s.str.: Ulvales and Ulotrichales sensu Mattox et Stewart (Fig. 1). The Ulvales were subdivided into five clades named Desmochloris, Halofilum, Phaeophila, Ulva, and Ctenocladus. In addition, a few single lineages (Bolbocoleon piliferum and Pseudoneochloris marina) were also members of the Ulvales. The Ulotrichales was split into two clades (Acrosiphonia and Planophila). All clades and lineages were highly supported in all bootstrap and Bayesian analyses. The non-marine ulvophytes belonging to the Ulvales represented six lineages (= genera; see below), which were highly supported in all phylogenetic analyses. In contrast, those belonging to the Ulotrichales were distributed in the Planophila-clade, which could not be clearly assigned to genera using solely SSU rDNA sequences. As shown in Fig. 1, most generic affiliations of the investigated strains were distributed in different clades and were often not closely related. For example, the strains named Dilabifilum ssp. (marked with an * in Fig.1) belonged to five lineages among the Ulvales. Even the assignment of the strains at the species level occurred in different phylogenetic groups, and these taxa were often closely related to strains that were originally identified as members of other genera. As an example within the Ulotrichales, the authentic strains of Pseudendoclonium basiliense and its variety brandii (marked with # in Fig.1) were closely related to those of Chamaetrichon and Rhexinema, respectively. Another strains assigned as Pseudendoclonium basiliense (also marked with #) even represented own lineages.
To gain better phylogenetic resolution, we analyzed SSU and ITS rDNA sequences of the non-marine ulvophytes separately in two concatenated datasets (Ulvales and Ulotrichales; Figs 2-3). The SSU and ITS rDNA sequences were aligned according to their secondary structures.
The investigated strains belonging to the Ulvales (Fig. 2) were split into five lineages representing genera (Pseudendoclonium, Halofilum gen. nov., Paulbroadya gen. nov., Lithotrichon gen. nov., Ctenocladus; see details below). All clades were highly supported by different Bayesian (PHASE and MrBayes) and bootstrap (ML, RAxML, NJ, and MP) methods. Strains that had been previously assigned to the genus Dilabifilum were distributed in almost all lineages partly together with species of other genera, demonstrating the polyphyly of Dilabifilum. The authentic strains of D. arthopyreniae (SAG 467-2) and D. incrustans (CCAP 415/1) formed together with Pseudendoclonium submarinum, the type species of this genus, a monophyletic lineage (Pseudendoclonium). In contrast, the authentic strain of D. prostratum (SAG 23.92 = CCAP 415/4) was not closely related to that lineage and represented together with two unidentified Dilabifilum isolates, its own clade (Paulbroadya). D. printzii (SAG 467-1) was positioned together with strains designated Ctenocladus circinnatus in another lineage of the Ulvales (Ctenocladus). Other strains of Dilabifilum formed, together with strains assigned as Pirula salina, an alga that reproduced by budding in a monophyletic group (Halofilum gen. nov.; see below). Strain SAG 2038 showed no affiliation with one of the other clades and was a single member of the newly described genus Lithotrichon (see below "Taxonomic implications").
All other strains investigated in this study belonged to the order Ulotrichales (Fig. 3). In contrast to the results obtained for the SSU rDNA phylogeny (Fig. 1), which showed a weak resolution within this order, the phylogenetic analyses of the concatenated dataset resulted in another scenario. Seven lineages (Sarcinofilum gen. nov., Ulothrix, Rhexinema, Chamaetrichon, Tupiella gen. nov., Vischerioclonium gen. nov., and Planophila) could be clearly distinguished among this order, which represented the genera discussed in detail in the section "Taxonomic implications". All clades were highly supported in all of our analyses. Similar to the situation described above for Dilabifilum, the strains designated with the same generic and species names occurred in different lineages mixed together with members of other genera. For example, isolates of Pseudendoclonium basiliense and its variety brandii could be found either in the Chamaetrichon and Rhexinema clades or could form their own lineages (Tupiella and Vischerioclonium). Strains assigned to the Chamaetrichon capsulatum and Gloeotilopsis sarcinoidea occurred also in different lineages (Chamaetrichon and Rhexinema clades). Only the strains identified as members of the genera Trichosarcina (Sarcinofilum gen. nov.; see below) and Planophila are not mixed with other taxa and form monophyletic lineages.
Species delimitation using ITS-2/CBC approach As shown in Figs 2 and 3, all lineages representing genera of the Ulvales and Ulotrichales were highly supported in all phylogenetic analyses. To support the molecular differentiation at generic and species levels, we analyzed the secondary structures of SSU and ITS-2 rRNA sequences. The secondary structures of all SSU sequences used for analyses presented in Figs 2-3 were compared with those shown in Fig. S1 of Ulothrix zonata (SAG 38.86). The two orders Ulvales and Ulotrichales as well as each genus were highly supported by synapomorphies in the secondary structures (data not shown). Within the highly supported genera the phylogenetic analyses (Figs 2-3) revealed several subclades, which represent species. For example, four separated lineages were observed in Pseudendoclonium, which are also highly supported in all analyses. Similar is the situation for the genera Halofilum, Paulbroadya, Ctenocladus, Rhexinema, and Planophila. All subclades among these genera are highly supported. Only within the genus Chamaetrichon the subdivision into lineages is not supported.
For species delimitation among these genera, we used the ITS-2/CBC approach, which were introduced by Demchenko et al. (2012), Darienko et al. (2015Darienko et al. ( , 2016 for several groups of green algae. This approach relies on complete and accurate ITS-2 rDNA sequences without ambiguities, which then were folded using the constraints and methods described in Material & Methods above. Using these constraints all programs resulted in almost identical secondary structures of all ITS-2 sequences (only minor differences in G•U/U•G base pairs, which thermodynamically less stable fold in mfold than in the stochastic approach using CONTRAfold). The ITS-2 secondary structures of all investigated strains are very conserved and have three helices (Helix I-III sensu Mai and Coleman 1997), Helix IV is missing (see Figs S2). The conserved regions of the ITS-2 secondary structures were extracted and translated into a number code as described above in Material & Methods. The number codes of strains belonging to one genus were compared to detect compensatory base changes for species discrimination. As summarized in Table 1, the subdivision within all genera into subclades as shown in Figs 2-3, which represent species, was supported by CBCs and HCBCs in the conserved region of ITS-2. For example, the presence of 12 CBCs and 5 HCBCs supported the split of Pseudendoclonium into four species. For each species a unique barcode could be observed (see Figs S2).

ULVO-18 (C. circinnatus)
SAG 467-1 (D. printzii) C. printzii comb. nov. . Molecular phylogeny of the Ulvales sensu Mattox and Stewart based on SSU and ITS rDNA sequence comparisons. The phylogenetic trees shown were inferred using the maximum likelihood method based on the data sets (2554 aligned positions of 29 taxa) using PAUP 4.0b10. For the analyses the best model was calculated by Modeltest 3.7. The setting of the best model was given as follows: GTR+I+G (base frequencies: A 0.2245, C 0.2728, G 0.2822, T 0.2204; rate matrix A-C 1.2613, A-G 1.7439, A-T 1.5854, C-G 1.1603, C-T 3.7924, G-T 1.0000) with the proportion of invariable sites (I = 0.5454) and gamma shape parameter (G = 0.6998). The branches in bold are highly supported in all analyses (Bayesian values > 0.95 calculated with PHASE and MrBayes; bootstrap values > 70% calculated with PAUP using maximum likelihood, neighbor-joining, maximum parsimony and RAxML using maximum likelihood). The original designation of each strain is given in brackets after the strain number.  * * * ** * FIGURE 3. Molecular phylogeny of the Ulotrichales sensu Mattox and Stewart based on SSU and ITS rDNA sequence comparisons. The phylogenetic trees shown were inferred using the maximum likelihood method based on the data sets (2355 aligned positions of 33 taxa) using PAUP 4.0b10. For the analyses the best model was calculated by Modeltest 3.7. The setting of the best model was given as follows: GTR+I+G (base frequencies: A 0.2485, C 0.2314, G 0.2668, T 0.2534; rate matrix A-C 1.5764, A-G 3.1118, A-T 1.7950, C-G 0.7531, C-T 7.2031, G-T 1.0000) with the proportion of invariable sites (I = 0.7371) and gamma shape parameter (G = 0.4509). The branches in bold are highly supported in all analyses (Bayesian values > 0.95 calculated with PHASE and MrBayes; bootstrap values > 70% calculated with PAUP using maximum likelihood, neighbor-joining, maximum parsimony and RAxML using maximum likelihood). The original designation of each strain is given in brackets after the strain number. The branches marked with * and ** were reduced in length to 25% and 10%, respectively.

ULVO-1 (Planophila bipyrenoidosa)
All species of the other genera mentioned in Table 1 were also supported by CBCs and HCBCs in the ITS-2 sequences with one exception. The two species of Paulbroadya had similar ITS-2 sequences with little variations (9.6%), and no CBC/HCBC could be discovered; however, in contrast to ITS-2 they showed eleven CBCs and four HCBCs in the SSU sequences. The strains belonging to Chamaetrichon, which showed no resolution within the genus using SSU and ITS (see Fig. 3), could also not be subdivided into groups using the ITS-2/CBC approach. Only two HCBCs were discovered among the strains. Therefore, the separation into different species within Chamaetrichon was not supported.
Morphology and identification of the investigated strains As described above, the investigated strains were assigned to genera and species, which do not correspond to their phylogeny presented in Figs 1-3. This raises the question of whether these strains were misidentified or the features for identification were too variable or missing. To answer this question, we studied the morphology of all strains under different growth conditions, as described in Material & Methods. The morphology of all authentic strains was consistent with the original species descriptions, and all assignments at species level in Fig. 1 are correct with one exception. The strain SAG 29.93 designated as Gloeotilopsis planctonica did not fit with the original species description provided by Iyengar & Philipose (1956). This strain could be identified as Pleurastrum paucicellulare using the key of Ettl & Gärtner (1995).
All strains of the Ulotrichales had a similar morphology: cell packages with different tendencies to form branched pseudofilaments, uniserial or sometimes biserial filaments, often embedded in common mucilage. Details about the morphological features are described in the section "Taxonomic implications". Some features such zoospore formation could not be observed in all strains. All investigated strains showed a high phenotypic plasticity as demonstrated in Figs 4-23, which highlighted the difficulties related to identification at generic and species levels.
The investigated members of the Ulvales are mostly short or long branched filaments, with each cell having a plate-like chloroplast and a pyrenoid, often forming within the middle of the thallus a pseudoparenchymal plate. The differences between genera are not clear: special branching and long cells by Dilabifilum or short branched, easily breaking down filaments by Pseudendoclonium. All investigated authentic strains of Ulvales correspond to the type descriptions, except for Pseudendoclonium printzii, which no longer forms filaments. All attempts to stimulate filament formation, such as growth in different media, a short transfer cycle, and different temperatures were unsuccessful.
Another exception are strains previously assigned to the Pirula. Both investigated strains characterized by special reproduction of budding, containing parietal chloroplasts with a single pyrenoid and correspond to the type description of Heterogonium salinum (Dangeard 1911(Dangeard , 1912).

Molecular phylogeny of non-marine Ulvophyceae
Our investigations of terrestrial and freshwater green algae have revealed that all of them belong to the Ulvophyceae. The species identification and their affiliation to the Ulvophyceae is often very difficult and can be only performed by studying of strains in culture under different conditions to discover all life stages. The typical characteristics of the Ulvophyceae are mostly ultrastructural features, such as the counterclockwise orientation of the basal bodies in the flagellated cells and the type of cytokinesis (Mattox & Stewart 1984, Sluiman 1989; see also review of Pröschold & Leliaert 2007). The only clear characteristic of Ulvophyceae, which can be observed by light microscopy, is the occurrence of a "Codiolum"-stage (zygote) during sexual reproduction (Kornmann 1973). For Ulothrix zonata, a "Codiolum"-stage has been observed by Dodel (1876). However, for most freshwater and terrestrial ulvophytes, the sexual reproduction is unknown. Therefore, the molecular phylogeny of DNA sequences (SSU, ITS rDNA or rbcL) is used for most of the recent investigations studying Ulvophyceae. New lineages could be discovered by those analyses. For example, Watanabe & Nakayama (2007) have revealed that two freshwater and terrestrial green algae originally considered to be chlorophytes, belong to the ulvophytes (Ignatius tetrasporus, Pseudocharacium americanum). Skaloud et al. (2013b) have demonstrated that coccoid green algae of the genus Scotinosphaera (previously known as Kentrosphaera) are members of the Ulvophyceae s.lato. Our phylogenetic analyses of the Ulvophyceae s.str. presented in Fig. 1 showed that two major lineages of the Ulvophyceae contain non-marine strains: Ulvales and Ulotrichales sensu Mattox and Stewart. In contrast to the domination of these orders by marine species, our study clearly revealed that the biodiversity of non-marine taxa among these groups are much higher than expected. These strains investigated in our study were distributed in five and seven genera of the Ulvales and Ulotrichales, respectively. Five out of them are newly discovered. The high biodiversity was also confirmed by Wetherbee & Verbruggen (2016), who recently described a new genus (Kraftionema) among the Ulvophyceae. As shown in Fig. 1, this genus is a member of the Ulotrichales, which is closely related to Rhexinema. Liu et al. (2016) collected samples of Ctenocladus from two lakes in Tibet, China. These are closely related to our Ctenocladus circinnatus in SSU phylogeny. However, they differ in SSU sequences to our investigated strains. Unfortunately, no ITS sequences of the Chinese samples were available, and no strains have been deposited in public culture collections. Therefore, these strains cannot be affiliated at the species level, but it seems that they belong to a third species of Ctenocladus.
Species concept among non-marine ulvophytes using the ITS-2/CBC approach Many species and genera are traditionally described using the morphological species concept. However as highlighted above, this concept is artificial because of the high phenotypic plasticity. As a consequence we applied the ITS-2/CBC approach for species delimitation. This approach has been used for several green algal genera (see Darienko et al. 2016 and references therein) and takes the occurrence of compensatory base changes in the conserved region of ITS-2 into account for species differentiation. Coleman (2009) has demonstrated that if two specimens of a monophyletic lineage have at least one CBC in this region of ITS-2 they cannot mate and belong to different biological species. We applied this approach to the twelve highly supported genera of the Ulvales and Ulotrichales (see Figs 2-3) and recognized 24 species, almost all of which differ from each other in at least in one CBC. Only the two species of Paulbroadya have no CBC in ITS-2, but eleven in SSU (Table 1). The translation into number-coded alignment of the conserved ITS-2 region allows an easy recognition of CBCs and HCBCs, as demonstrated in Figs S2 for each genus.
As shown in Table 1, the genetic variability of the genera differs in both orders of the Ulvophyceae. Whereas the genera Pseudendoclonium, Halofilum, and Ctenocladus (Ulvales) have more than 30% variable positions within ITS-2, those of the Ulotrichales vary a maximum of 26% (Rhexinema). Most of the others have only 10-16% variable positions. Despite different evolutionary rates among the genera, the ITS-2/CBC approach could distinguish species within each genus in our study. Therefore, this approach is probably applicable for species delimitation of all Ulvophyceae.

Historical overview and taxonomic implications
As shown in the figures and tables above, investigations of isolated strains require many taxonomic changes and description of new genera and species, which will be discussed in detail in the following chapters. Most taxonomic problems occurred because of a similar morphology with a high phenotypic plasticity among the investigated strains. In particular, the morphological changes caused different taxonomic classifications depending on various salinities. Even the classification at higher levels (families and orders) remain unresolved and require further studies. In the meantime, we are using the system introduced by Mattox and Stewart (1984) and modified by O` Kelly and Floyd (1984) and Sluiman (1989). At present we have not revised the system at the order and family levels but only at the generic and species levels of non-marine ulvophytes:

The order Ulvales sensu Mattox and Stewart Pseudendoclonium, Pseudopleurococcus, or Dilabifilum, how we should name them?
The genus Pseudendoclonium with its type species P. submarinum was described by Wille (1901). The type locality of this species was a floating wooden piece on coastal water in Drøbak (Norway). Since the first description, approximately 20 more species of Pseudendoclonium have been described from freshwater and marine habitats (John & Johnson 1989). Some of them were originally assigned to other genera. For example, Pseudendoclonium printzii (Vischer) Bourrelly was described as a member of the genus Pseudopleurococcus by Vischer (1933). Two species of Pseudopleurococcus (P. vulgaris and P. botryoides) were originally described by Snow (1899) from the bark of trees. Unfortunately, since the first description, no reports of both these species have been published. Therefore, the taxonomic status of this genus remains unresolved. Both genera, Pseudendoclonium and Pseudopleurococcus, have a similar morphology and differ only in the lack of zoospore formation in Pseudopleurococcus. Vischer & Klement in Vischer (1953) described another species of Pseudopleurococcus, P. arthopyreniae, which is a photobiont of the lichen Arthopyrenia kelpii. Tschermak-Woess (1970) discovered on the cultured type material of this species zoospores and transferred this species together with the other species P. printzii and P. incrustans, which were also described by Vischer (1956), to the newly erected genus Dilabifilum. Broady & Ingerfeld (1993) isolated D. prostratum in epilithic crusts on Ross Island (Antarctica). Johnson & John (1990) questioned the establishment of Dilabifilum based on comparative studies of cultured material. They found that the diagnostic features were very variable, which demonstrated the high phenotypic plasticity among the species of Dilabifilum. Thüs et al. (2011) discovered that many photobionts of the lichen family Verrucariaceae belong to the genus Dilabifilum, some of which were investigated herein.
In our study, we analyzed almost all available strains including the authentic strains of the above described species, which were designated members of the three genera. The phylogenetic analyses of SSU and ITS rDNA sequences as well as the ITS-2/CBC approach (Figs 1-2, Table 1) clearly demonstrated that the three genera are polyphyletic. Unfortunately no type strain of Pseudendoclonium submarinum is available; however, Mullins (2007) sequenced the SSU rDNA of a strain that was isolated by Ruth Nielsen from the type locality and compared the morphology with the original description. He concluded that this material fits the original diagnosis of Wille. As shown in Fig. 1 Pseudendoclonium submarinum is closely related to Dilabifilum arthopyreniae and D. incrustans as well as several unidentified Dilabifilum strains. Only D. printzii belongs to another genus (Ctenocladus; see below). The strain SAG 2038 designated Dilabifilum sp. is also not closely related to this group and represents a new genus (see below). As a result of these findings the following nomenclatural changes are necessary.    Epitype (designated herein in support of the iconotype): The authentic strain SAG 23.92 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
Comment: This species is probably not endemic in Antarctica. ITS-2 DNA Barcode: PAU1 in Figs S2. The thalli of mature plants are cushion-shaped, composed from prostrate and branched filaments, with a maximum length of 2-3 mm. The prostrate system is formed of square cells that are often gathered into cell packages with cell size of 5.2-5.5-6.8 μm. The erect system is richly branched uni-or bilateral. Intercalary cells of erected filaments 5.5-10.5 μm long × 5.2-6.8 μm, up to twice as long as broad. Terminal cells are slightly pointed, 14.5-21.2 μm long × 4.8-5.2 μm wide, and are twice to four times as long as broad. Cells are uninucleate, with parietal plate-like chloroplast and one pyrenoid. The pyrenoid is surrounded by starch grains. Asexual reproduction occurs by formation of zoospores. Zoosporangia are pear-shaped and usually produced in the prostrate system of filaments. Zoosporangia 11.2-21.2 μm long × 5.5-8.1 μm wide. Zoospores are released by rupture of sporangia on the broad side of sporangia. Zoospores are quadriflagellated, very small (4.5-5.0 × 3.7-4.0 μm), with an anterior stigma. The species differs from similar species by SSU-ITS sequences. Habitat: Symbiont of Verrucaria mucosa. Type locality: Roscoff, Brittany, France. Holotype (designated herein): The authentic strain SAG 2240 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
Iconotype (designated herein to support of the holotype): Fig. 8 in this study. Etymology: The species named in the honor of Dr. Akira Peters, who provide us the strains of Verrucaria photobionts.
Comment: This species is distributed at least in the cold water of the North Atlantic as photobiont of Verrucaria mucosa: SAG 2240 -Roscoff, Brittany, France and ULVO-34 -Oban, Scotland.
ITS-2 DNA Barcode: PAU1 in Figs S2 (barcode is identical with P. prostrata, but differ in SSU rDNA sequences).

Lithotrichon Darienko et Pröschold gen. nov.
Diagnosis: The thalli of mature plants are cushion-shaped, composed of prostrate and branched filaments. The prostrate system consists of rounded sarcinoid-like packages. The branched filaments are short and appear on the margin of the prostrate system. Vegetative cells contain parietal plate-like chloroplasts with a pyrenoid. Reproduction occurs by vegetative division and by zoospores.
Lithotrichon pulchrum Darienko et Pröschold sp. nov. (Fig. 9A-I) Diagnosis: Plants in liquid 1/2 SWES medium up to 0.5 mm consist of prostrate and erected filaments. The system of prostrate filaments is very prominent and is formed from three-dimensional packages. The vegetative cells of the prostrate system are rounded or compressed from the sides, 5.9-8.8 μm in diameter, with a thick cell wall. Vegetative cells usually contain one or two large vacuoles. The erect system formed from short filaments consists of several cells (max. 10 cells). The end cells of plants are cylindrical, sometimes curved, 12.0-23.5 μm long × 3.5-5.5 μm wide and generally 2-4 times longer than broad. Branching is mostly bilateral. Cells are usually uninucleate, but sometimes the longest cells contain two nuclei and two pyrenoids (state before dividing?). Chloroplasts are parietal, usually filling the cell, with a pyrenoid. Zoosporangia are oval and approximately 16.2 μm in diameter, containing 8 zoospores. Zoospores are ovoid, 7.0-7.5 μm long × 4.0-4.5 μm wide with an anterior stigma. Zoospores are released by sudden fracture of the cell wall.
Holotype (designated herein): The authentic strain SAG 2038 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
Iconotype (designated herein in support of the holotype): Fig. 9 in this study. ITS-2 DNA Barcode: LIT1 in Figs S2.

Pirula versus Heterogonium
The genus Pirula with its type species P. gemmata was originally described by Snow (1911Snow ( , 1912. She observed this species from samples collected in Switzerland and Guatemala. Printz (1927) transferred another species to Pirula, which was described by Dangeard (1911Dangeard ( ,1912 as Heterogonium salinum from a marine habitat. Pascher (1939Pascher ( , 1944 synonymized the type species of Pirula with Heterococcus, a xanthophycean genus, based on the lack of a pyrenoid and the presence of several chloroplasts per cell. The taxonomic change of Heterogonium salinum to Pirula is not supported. This transfer was also questioned by Gayral and Lepailleur (1969) because of differences in morphology and ecology (freshwater versus marine). However, the generic name Heterogonium is already preoccupied for a tropical fern species by Presl (1851). Therefore, for the species found by Dangeard, the new generic name Halofilum is proposed (see below). In addition, several strains originally assigned as Dilabifilum sp. are closely related to this species and represent new species, which will be erected below.   Habitat: unknown Type locality: unknown (only known from a culture vessel containing sea water). Lectotype (designated herein): Fig. 1 in Dangeard (1911). Epitype (designated herein): The strain SAG 1.95 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
ITS-2 DNA Barcode: HAL1 in Figs S2. Comment: The formation of short filaments was observed only on SWES agar plates under an inverted microscope. The filaments are very fragile and immediately disintegrate by preparation on a microscopy slide.  Diagnosis: Filaments are very short, usually not more than 2-8 cells. The filaments are branched, very fragile and easily disintegrate. They can be observed only in very young cultures (not older than several days). After one week of cultivation on the fresh medium, they occur as solitary cells. Cells are pear-shaped with a relatively thick cell wall. The chloroplast is parietal and usually covers 2/3 of the cell. The pyrenoid is present and surrounded by 2-4 large starch grains. Single vegetative cells are 8.0-10.0 μm long × 5.0-6.0 μm wide and uninucleate. Vegetative cells of filaments sometime can reach 14.0-20.0 μm × 4.5-5.0 μm. Reproduction occurs by budding. Differs from other species by SSU-ITS sequences and reproduction by budding. Habitat: from an enrichment culture of Rhizoclonium riparium.

Halofilum helgolandicum
Type locality: Heligoland, Germany. Holotype (designated herein): The strain SAG 2.95 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
Iconotype (designated herein in support of the holotype): Fig. 11B in this study. ITS-2 DNA Barcode: HAL2 in Figs S2.
Halofilum ramosum Darienko et Pröschold sp. nov. (Fig. 11D-G) Diagnosis: Filaments are relative long, consisting of 20-100 cells, richly branched and curved. The cells of primary branches are slightly shorter, equal to or to twice as long as broad; cylindrical or square; 7.8-12.5 μm long × 6.9-8.5 μm wide. The secondary branches appear laterally or bilateral. The terminal cells of secondary branches are cylindrical, often pointed, up to 5 times longer as broad. Cells are 16.0-28.0 μm long × 5.6-7.2 μm wide. The longest terminal cells very often contain 2-3 pyrenoids and nuclei. Such cells probably represent some special stage of vegetative dividing. In the primary filaments, irregular cells containing up to 4 pyrenoids were observed. The cells later formed package-like structures, and from these cells the secondary branches often arise. Reproduction by budding or by zoospores was not observed.
Differs from other species by SSU-ITS sequences and the absence of reproduction by budding. Habitat: marine, photobiont of Wahlenbergiella striatula. Type locality: Wales, Anglesey (Ynys Mon), Porth Trecastel, in stone cracks of coastal rocks. Holotype (designated herein): The strain SAG 2050 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
Iconotype (designated herein in support of the holotype): Fig. 11F in this study. ITS-2 DNA Barcode: HAL3a/b in Figs S2. Comment: This species is probably widely distributed as photobiont and free-living. Additional strains: SAG 2235 and ULVO-28 were isolated from Verrucaria maura, Roscoff, Brittany, France and ULVO-19 was isolated from a green crust on the wall of ruins in Carthage, Tunisia (see Hoffmann & Darienko 2010).
Note: The budding-like reproduction of Halofilum is quite rare among microalgae and has only been reported for few green algal genera, which belong to the Trebouxiophyceae (Pseudomarvania, Eliaš & Neustupa 2009;Marvania, Nannochloris, Yamamoto et al. 2007).

Ctenocladus versus Lochmiopsis
The genus Ctenocladus described by Borzi (1883) is from a marine habitat. The characteristic morphological feature of the type species C. circinnatus is the one-sided branching of the filaments. Ctenocladus is so far known as a rare species. Only few records have been published (Blinn & Stein 1970;Herbst & Castenholz 1994). Only one strain of C. circinnatus has been isolated and deposited in a public culture collection (CCMP 2158). However, this strain does not show the typical morphology of this genus in culture. In our study, this strain is almost identical in sequences with strains that were isolated from sandstone, and salt marshes at high carbonate concentrations (solonetz-solonchak). The latter habitat is typical for the genus Lochmiopsis, which was described by Woronichin & Popova (1929) from soda lakes in Siberia (Russia). This genus was also recorded from solonetz-solonchak soils in different Asian deserts (Novichkova-Ivanova 1984). Ruinen (1933) has demonstrated that L. sibirica has high phenotypic and ecological plasticity. She showed that material from the type locality and from California has similar morphology and ecology. Based on her findings, Smith (1950) transferred this genus Lochmiopsis as a later synonym of Ctenocladus, which is currently accepted by most phycologists (Blinn & Stein 1970). Our investigations showed similarities and differences in morphology and ecology to those of both genera. Unfortunately, no authentic material of both genera are available in culture collections. Therefore, the taxonomic status remains unclear. However, as our study has demonstrated the type strain of Pseudopleurococcus printzii is closely related to the investigated strains mentioned above. As a consequence, we propose as a compromise the usage of the generic name Ctenocladus until material of both genera collected from type localities has been investigated.   Lectotype (designated herein): Fig. 11: 3 in Vischer (1933).
Epitype (designated herein in support of iconotype): The authentic strain SAG 467-1 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.

The order Ulotrichales sensu Mattox and Stewart
The genus Trichosarcina The genus Trichosarcina was described by Nichols & Bold (1965) from shallow pool in granite rocks at Enchanted Rock and Balanced Rock in Texas. The algae is characterized by initial uniserial filaments become pluriserial with time. The other interesting peculiarity is zoosporogenesis. Only one quadriflagellated zoospore was produced per vegetative cell. Unfortunately, the name T. polymorpha is invalid because the type was not designated, and generic and species were described in one diagnosis (descriptio generico-specifica, Art. 38.5, ICN). Chappell & O'Kelly (1991) performed the ultrastructural investigation of Pseudoschizomeris mucosa Broady and discovered that this alga belong to the genus Trichosarcina (T. mucosa (Broady) Chappell et O'Kelly). Thompson & Wujek (1996) transferred both species to Filoprotococcus Kufferath with the type species Filoprotococcus enteromorphoides Kufferath, which was originally found in lotic water in Luxembourg. They found this alga in the marshy area near Kansas (USA) as an epiphyte growing on Tolypella nidifica var. glomerata. The authors highlighted that this alga has some clear differences in comparison to T. polymorpha, which are two times larger in cell size and produce 2-4 zoospores per cell.
Unfortunately, no information about the number of flagella was provided. Other differences between both genera are the absence of a pyrenoid in Filoprotococcus.
We studied several isolates, including the authentic strains of Trichosarcina polymorpha and T. mucosa. All strains are morphologically very similar and have almost identical SSU and ITS rDNA sequences, thus belonging to one species. Unfortunately, the genus Trichosarcina has not been validly described, and consequently all later combination are also invalid. For a valid publication of genera and species described according to Art. 38.5, three criteria have to be fulfilled. Whereas the first two criteria have been satisfied (monotypic genus at the time of publication, new species, not no combination), the last about the clear typification has not been clarified in Nichols & Bold (1965). Then on or after 1 st January 1958 of the name of a new taxon of the rank of genus or below is valid only when the type of the name is indicated (Art. 40.1, ICN). Nichols & Bold (1965) investigated this species from two collections (1960 and 1961), but they did not designate any of the two as type. Therefore, this genus and species is invalid. As a consequence, we propose the following new genus. Asexual reproduction occurs through fragmentation of the filaments or special zoosporogenesis. Quadriflagellated zoospores develop into the vegetative cells of pluriserial filaments. Each cell forms only one zoospore. Sexual reproduction is not observed.

Sarcinofilum
The phylogenetically closely related genera differ by presence of pluriserial filaments and by differences in SSU-ITS sequences.

The genera Planophila Gerneck and Pseudendocloniopsis Vischer
The genus Planophila (with its type species P. laetevirens) was described by Gerneck (1907) from soil sample with moss protonema. Later, several more species of this genus were proposed. Reisigl (1964) described Planophila bipyrenoidosa from alpine chalk soils. This alga differs from the type species by having a smaller cell size and containing 1-3 pyrenoids. P. terrestris was described by Groover & Hofstetter (1969). Broady (1982) isolated two strains of Planophila A and B from Iceland and Antarctica, respectively. Dangeard (1965) described a new species Ulvella microcystoides, which was later transferred to Planophila by Kornmann & Sahling (1983). Friedl & O'Kelly (2002) revised the genus Planophila based on SSU phylogeny and TEM. They confirmed that Planophila laetevirens is a member of Ulvophyceae and is not close related to the Planophila A and B of Broady. Planophila A was transferred to the newly erected genus Pabia by Friedl & O'Kelly (2002), and was later synonymized with Pseudochlorella by Darienko et al. (2016). Friedl & O'Kelly (2002) also discovered that Planophila terrestris is a member of the Chloropeltidales and established a new genus Floydiella. They also proposed a new genus Dangemannia for Planophila microcystoides, which was later corrected as Neodangemannia by Wynne & Funari (2014). Friedl & O'Kelly (2002) also discovered that the monotypic genus Pseudendocloniopsis (type species: P. botryoides), which was described by Vischer (1933), is closely related to Planophila. Printz (1964) transferred the genus Filoprotococcus to Pseudendocloniopsis; however, this combination is invalid because the name Filoprotococcus is older.
In our study, we investigated seven strains that could be clearly identified as P. laetevirens and P. bipyrenoidosa. For both species, we proposed the following lectotypes and epitypes.

Rhexinema versus Pleurastrum and Gloeotilopsis
The genus Rhexinema was described by Geitler (1942) to separate Pleurastrum paucicellulare from other species of this genus based on the following morphological criteria: very short branched filaments that easily disintegrate, parietal chloroplasts with a pyrenoid, and biflagellated zoospores. P. paucicellulare was originally described by Vischer (1933) from neustons in stagnant water near Basel, Switzerland (authentic strain SAG 463-1). Tupa (1974) did not support Rhexinema and left this species with Pleurastrum, in contrast to Lukešová (1991) and Ettl & Gärtner (1995), who accepted the genus as described by Geitler. Friedl (1996) used phylogenetic analyses of SSU rDNA sequences to determine the polyphyly of the genus Pleurastrum and demonstrated the close relationship of Pleurastrum paucicellulare (SAG 463-1) with Protoderma sarcinoidea (UTEX 1710) and Gloeotilopsis planctonica (SAG 29.93). On this basis, he proposed the new combinations of Gloeotilopsis paucicellulare and G. sarcinoidea. Unfortunately, as demonstrated in our study, the identification of the strain SAG 29.93 was incorrect and did not fit with the original description by Iyengar & Philipose (1956). Therefore, all other combinations with Gloeotilopsis must be changed. Despite the different opinions about the genus Rhexinema by Tupa (1974), Geitler's proposal was based on the authentic material of Vischer for Pleurastrum paucicellulare. Therefore, the genus Rhexinema has been validly described, and we proposed the following new combinations and species. Interestingly, several strains assigned as species of other genera also belong to Rhexinema. The authentic strain of Pseudendoclonium basiliense var. brandii and a strain identified as Helicodictyon planctonica are also members of Rhexinema. Both strains exhibit a morphology similar to their original descriptions by Vischer (1933) and Whitford & Schumacher (1966), as demonstrated in our study. Emended diagnosis: The filaments are very short consisting of 2-10 cells or 2-dimensional cell packages embedded in common mucilage. Branching is rudimentary. Vegetative cells are cylindrical, often curved, and uninucleate, with a parietal chloroplast containing one pyrenoid surrounded by starch grains. Reproduction occurs by vegetative division, and biflagellated zoospores possess a stigma and two contractile vacuoles.  Whitford (1956Whitford ( , 1960 and Whitford & Schumacher (1966). Other species of Rhexinema differ by a Chlorosarcinopsis-like morphology and by SSU-ITS sequences.
Habitat: lateritic soil. Type locality: Brazil, central part of Sao Paulo State, Sao Carlos, Itirapina and Pirissanunga County, elevation of about 800 m a.s.l., field of sugar cane, dense canopy, without any ground layer.
Holotype (designated herein): The strain ULVO-10 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.
ITS-2 DNA Barcode: RHE4 in Figs S2. Darienko et Pröschold sp. nov. (Fig. 16F-G, 20A-G) Diagnosis: Algae occurring as short 2-8-celled curved filaments, solitary or forming pseudofilaments of 2celled packages held together by the remaining old cell walls. The cells are embedded in mucilage. Branching is very rudimentary and rare. The end cells of the rudimentary branches are ovoid or pear-shaped. Single cells are ovoid, oval or round with a diameter of 8.0-9.3 μm. Cells in packages are compressed from the sides, and have a diameter of 8.0-11.3 μm. End cells of rudimentary branches are 11.5 μm × 8.0 μm. Cells are uninucleate with parietal chloroplasts containing one good visible pyrenoid surrounded by several starch grains. Reproduction occurs by vegetative division. Zoospores are not observed.

Rhexinema sancta-tomea
Other species of Rhexinema differ by SSU-ITS sequences. Habitat: Mud. Type locality: São Tomé and Príncipe. Holotype (designated here): The strain ACOI 592 is permanently cryopreserved in a metabolically inactive state (cryopreserved in liquid nitrogen) in the SAG, University of Göttingen, Germany.

Hazenia versus Chamaetrichon
The genus Hazenia (with the type species H. mirabilis) was described by Bold (1958) from a pool at Couchville Pike, Tennessee. This alga is characterized by short, irregularly branched filaments surrounded by mucilage. The cells are short and cylindrical with parietal chloroplasts containing pyrenoids with several starch grains. Asexual reproduction occurs through fragmentation of filaments. Sexual reproduction occurs by biflagellated isogametes. Zygotes with multilayered cell walls were also observed. Skaloud et al. (2013a) described a new species, H. broadyi, from a shallow lake near Anderssen Point in Antarctica. They also proposed a new combination H. basiliensis (previously Pseudendoclonium basiliense). The genus Chamaetrichon was described by Tupa (1974). The type species C. capsulatum was found on the liverwort, Pallavicia lyelli submerged in a shallow drainage area of Double Lake in Sam Houston National Forest (Texas). Our study revealed that the authentic strains of these taxa have a similar morphology and are phylogenetically very closely related. However, other strains assigned as Pseudendoclonium basiliense and Chamaetrichon capsulatum are not closely to these strains and were therefore described as new genera below. Unfortunately, the generic name Hazenia and its type species H. mirabilis was described in one diagnosis (descriptio generico-specifica, Art. 38.5, ICN) and no type was designated (Art. 40.1, ICN). The situation of the nomenclatural status is similar to those described above for Trichosarcina. The herbarium specimen of Hazenia deposited at Chicago Natural History Museum of this species was not indicated as type material (IRN 3565921, barcode C0172554F; Fieldmuseum.org). Therefore, this genus and species and all other proposed combinations are invalid. In contrast, the genus Chamaetrichon was validly published by designation of C. capsulatum as type species. As type for this species the culture DDT-8 (= UTEX 1918)  Diagnosis: The young thallus consists of an abundance of long branched filaments. Vegetative cells of young filaments are square with parietal chloroplasts, a single pyrenoid and a nucleus. End cells are slightly tapered or slightly pointed. The later thallus starts to form irregular rich prostrate and erect filaments. The mature thallus consists mostly of prostrate pluriserial filaments that easy disintegrate into cell packages, which form a short uniserial part consisting of several cells only at the ends. Vegetative cells in pluriserial filaments are rounded. Reproduction occurs via zoospores, akinetes and disintegrating filaments. Akinetes have thick cell wall without special ornamentation. Zoospore are quadriflagellated and lack a cell wall. Sexual reproduction is not observed.