Pseudendoclonium

Darienko, Tatyana & Pröschold, Thomas, 2017, Toward a monograph of non-marine Ulvophyceae using an integrative approach (Molecular phylogeny and systematics of terrestrial Ulvophyceae II.), Phytotaxa 324 (1), pp. 1-41 : 10-11

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.

Figures

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.