Settling the identity and phylogenetic position of the psychrotolerant green algal genus Coleochlamys (Trebouxiophyceae)

ABSTRACT

Despite significant recent advances, our understanding of the diversity and phylogeny of coccoid green algae remains incomplete, partly because of the existence of numerous previously described taxa that are yet to be reinvestigated to clarify their identity and phylogenetic position. An essentially forgotten taxon is the genus Coleochlamys Korshikov, presently classified in the class Chlorophyceae. Here we present the results of our investigations of one new and four previously available strains identified as Coleochlamys. Based on morphological features and molecular evidence, the strains represented two clearly differentiated species: Co. apoda, the type species of the genus, and Co. oleifera, which are both epitypified in this study. The two species differ in cell shape and presence or absence of a cell wall extension resembling a papilla. They are also differentiated by multiple compensatory base changes (CBCs) in the ITS2 region. Our data support the previous proposal that the genera Rhopalocystis and Fusochloris are later synonyms of Coleochlamys, and additionally suggest that the algae originally described as Characium perforatum K.W. Lee & H.C. Bold and Rhopalocystis cucumis are conspecific with Co. apoda. Phylogenies of both 18S rRNA and rbcL genes place Coleochlamys in the class Trebouxiophyceae, in a clade with Microthamnion. Analysis of environmental DNA data has revealed the existence of at least one additional Coleochlamys species, and of a closely related sister lineage (potentially a separate genus) encountered in an Alaskan glacier. The occurrence data on Coleochlamys indicate that the genus includes psychrotolerant algae that may be common in cold environments worldwide.

KEYWORDS:

• Distribution
• Green algae
• Phylogeny
• Polar
• Trebouxiophyceae

ACKNOWLEDGEMENTS

Two of the algal strains investigated in this study were isolated by the eminent Czechoslovak and Slovak phycologist Professor František Hindák, who passed away in 2019. We dedicate this paper to his memory. We thank Josef Elster for the Arctic field sample from which strain CAUP H 7402-CRYO was isolated, including the associated support from the Ministry of Education, Youth and Sports of the Czech Republic [LM2015078 CzechPolar2 Czech Polar Research Infrastructure and CZ.02.1.01/0.0/0.0/16_013/0001708 Ecopolaris]. We also thank John Cawley for proofreading the manuscript and correcting the English.

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the Grantová Agentura České Republiky [18-13458S].