Cladophora koktschetavensis from Kazakhstan is a synonym of Aegagropila linnaei (Cladophorales, Chlorophyta) and fills the gap in the disjunct distribution of a widespread genotype

Cladophora koktschetavensis is a filamentous freshwater alga of the order Cladophorales that has been described from Lake Shchuchie in Central-Northern Kazakhstan, which is currently the only known location of this species. Habitat and morphological characteristics of the type material of C. koktschetavensis strongly overlap with those of Aegagropila linnaei, and molecular sequences of ribosomal genes are virtually identical (small subunit (SSU) and large subunit (LSU) ribosomal RNA (rRNA) genes, internally transcribed spacer region 2 (ITS2)). Morphological and molecular evidence strongly suggests that the two species are conspecific, thus C. koktschetavensis is proposed as a taxonomic synonym of A. linnaei. The sequence of the highly variable ITS2 region was a perfect match to A. linnaei ribotype A. This ribotype had been shown previously to be widespread in the Northern Hemisphere, with most records from Japan and a few findings in Europe, Iceland and North America. The finding in Kazakhstan fills the gap between Japan and Europe in the disjunct distribution of this ribotype.

► Cladophora koktschetavensis is supposedly a freshwater alga endemic to Kazakhstan.
► We sequenced nuclear ribosomal genes to clarify the taxonomic status of the species.
► The ITS2 genotype of C. koktschetavensis matches one ribotype of Aegagropila linnaei.
► C. koktschetavensis is proposed as a taxonomic synonym of A. linnaei.
► This finding fills the gap in the previously disjunct distribution of this ribotype.