Diversity of the scenedesmacean genus Chodatodesmus (Chlorophyta) and new cryptic species in the algae flora of Lake Baikal revealed by an integrative approach

The genus Chodatodesmus belongs to the coccoid representatives of the family Scenedesmaceae with very scarce diagnostic traits. This genus includes two species, C. mucronulatus (the type species of the genus) and C. australis, which differ genetically. Until recently, data on the species diversity of Chodatodesmus and their biogeography were based on the study of a number of isolated strains.

Records of the species were limited to the aquatic ecosystems of Turkey, Peru, and Antarctica. Here, we characterized the new strains of Chodatodesmus, IRK-A 290 and 449, from Lake Baikal by combining morphological (LM, SEM, TEM) and molecular phylogenetic (SSU rRNA, ITS, rbc L, and tuf A) methods. The studied strains belonged to different species of the genus that were first recorded in Eurasia.

The strain IRK-A 290 was referred to C. australis, and IRK-A 449 was described as a new species Chodatodesmus intermedia sp. nov. For the analysis, we also used sequences from soil metagenomes obtained within the project on the global distribution of fungi and deposited in the Global Biodiversity Information Facility. Chodatodesmus nucleotide sequences were found in soils in different regions of the world.

This study showed that the majority of sequences from soil metagenomes refer to C. australis, and several sequences belong to the new phylogenetic clade of Chodatodesmus intermedia sp. nov. Sequences of C. mucronulatus were not detected in soils. The results obtained add to the data on the species diversity, morphology, genetic features, distribution, and occurrence of Chodatodesmus.