Phylogenetic relationships in Interfilum and Klebsormidium (Klebsormidiophyceae, Streptophyta).

Members of the genus Klebsormidium have cosmopolitan distribution and occur in a very wide range of freshwater and terrestrial habitats. Due to its simple filamentous morphology, this genus represents a taxonomically and systematically complex taxon in which phylogenetic relationships are still poorly understood. The phylogeny of Klebsormidium and closely related taxa was investigated using new ITS rRNA and rbcL sequences generated from 75 strains (isolated from field samples or obtained from culture collections). These sequences were analyzed both as single-marker datasets and in a concatenated dataset. Seven main superclades were observed in the analyses, which included sixteen well-supported clades. Some species of Klebsormidium, including the type species Klebsormidium flaccidum, were polyphyletic. Interfilum was recovered with high statistical support as sister taxon to a clade of Klebsormidium formed mainly by strains identified as K. flaccidum. Whereas some clades could be easily associated with described species, this was not possible for other clades. A new lineage of Klebsormidium, isolated from arid soils in southern Africa and comprising undescribed species, was discovered. Several morphological characters traditionally used for taxonomic purposes were found to have no phylogenetic significance and in some cases showed intra-clade variation. The capacity to form packet-like aggregates (typical of Interfilum), features of the morphology of the chloroplast and the type of habitat were the main phylogenetically relevant characters. Overall, Klebsormidium and Interfilum formed a more diverse algal group than was previously appreciated, with some lineages apparently undergoing active evolutionary radiation; in these lineages the genetic variation observed did not match the morphological and ecological diversity.

NEW STREPTOPHYTE GREEN ALGAE FROM TERRESTRIAL HABITATS AND AN ASSESSMENT OF THE GENUS INTERFILUM (KLEBSORMIDIOPHYCEAE, STREPTOPHYTA)(1).

Sarcinoid aeroterrestrial green algae were isolated from three arid locations in Ukraine and the Czech Republic. Although gross morphology suggested an affinity with Desmococcus (for taxonomic authorities, see Table S1 in the supplementary material), the cellular morphological characteristics were reminiscent of those of Geminella terricola. However, the presence of a complex of ultrastructural features indicated that these isolates were members of the streptophyte lineage in the green plants. 18S rDNA sequence phylogenies provided evidence of a close relationship with Klebsormidium in the Streptophyta, while the position of Desmococcus was within the Trebouxiophyceae. In the internal transcribed spacer (ITS) rDNA phylogeny, the sarcinoid isolates were closely related with strains of G. terricola and Interfilum paradoxum. Strains of that clade were morphologically united by a specific type of cell division that involves the association of persistent, cap-shaped remains of the mother cell wall with daughter cells. Consequently, these strains were assigned to a redefined genus Interfilum, and a new species, I. massjukiae, was described to accommodate one of the sarcinoid isolates. As the position of the genus Geminella was in the Trebouxiophyceae, the streptophyte G. terricola was transferred to Interfilum, as I. terricola comb. nov., but the ITS rDNA analyses proved inconclusive to resolve its affinities with other species of Interfilum due to intragenomic polymorphisms. The species of Interfilum had a closer relationship with K. flaccidum than with other species of Klebsormidium. The latter genus may not be monophyletic in its present circumscription.