Choosing an approach for identification of soil coccoid green microalgae (Trebouxiophyceae, Chlorophyta)

The article describes the morphological and molecular genetic approaches used to identify the green microalgae of the Trebouxiophyceae class from the ACSSI collection. In the brown semi-desert and chestnut soils, we found Muriella terrestris. In the buried meadow-chestnut soil we found Edaphochlorella mirabilis. Three more strains are characterized as new uncharacterized taxa: ACSSI 014 is a new species related to the genus Watanabea isolated from gray forest soil, with a pyrenoid surrounded by several starch grains, in contrast to the type species, and ACSSI 104 and 144 are a Nannochloris -like genus, whose representatives were found in solonetz and chestnut soil and are characterized by poor morphological specificities. It is shown that no single criterion (either morphological or other specificity, calculation of genetic distances, analysis and comparison of the ITS2 secondary structure, search for compensatory changes and molecular signatures) does not allow reliable classification of taxa. Therefore, due to this fact, it is necessary to apply a polyphasic approach in the systematics of algae, especially when identifying taxa with simple cellular morphology, which are often found in soils.