RESUMO
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.
