Overlooked diversity with terrestrial lifestyle in the predominantly freshwater and snow phylogroup Chloromonadinia (Volvocales, Chlorophyceae)
Abstract
The phylogroup Chloromonadinia (Volvocales, Chlorophyceae) encompasses ecologically versatile green microalgae with a predominantly freshwater and snow lifestyle. Although a few species have been described from soils, the evolutionary history of terrestrial volvocalean flagellates is poorly known due to undersampling.
Here we provide new insights into the phylogenetic position of terrestrial flagellates within the Chloromonadinia and investigate six unresolved strains from terrestrial and freshwater habitats in both hemispheres. The terrestrial strains differed in cell morphology, ultrastructure and lifestyle from the freshwater ones, therefore, we expected them to represent distinct evolutionary lineages (species or genera).
While the terrestrial strain SAG 25.87 (Chloromonas gracillima comb. & stat. nov.) from Czech mountains clustered within the psychrotolerant core Chloromonas clade, the other terrestrial strains formed a phylogenetically separate lineage which we proposed as Ostravamonas gen. nov. The new genus differs from other closely related Chloromonadinia genera by chloroplast, eyespot, papilla and cell-wall morphology.
Two terrestrial strains, CAUP G 1401 (coal spoil heap; Czechia) and SAG 12.72 (acidic soil; New Zealand), were designated as Ostravamonas chlorostellata comb. nov. and represent the first Chloromonadinia microalgae discovered in acidic terrestrial environments. Closely related 'Chlamydomonas' strains SAG 75.81 (ditch; France) and CCAP 11/108 (origin unknown) were reassigned to Ostravamonas meslinii comb. nov. and Ostravamonas tenuiincisa sp. nov., respectively.
Our study shows that the traditional 'Chlamydomonas' still hides an overlooked diversity of species with a terrestrial lifestyle that are nested phylogenetically within the Chloromonadinia phylogroup.