Coccomyxa cimbrica sp. nov., a green microalga found in association with carnivorous plants of the genus Drosera L.

Coccomyxa Schmidle (Trebouxiophyceae, Chlorophyta) is a genus of green microalgae that has worldwide distribution, with representatives found in a broad range of terrestrial and aquatic ecosystems. Members of this taxon can be free-living and/or associated with other organisms, establishing different types of relationships (e.g. parasitic, symbiotic). The most frequent organisms forming associations with Coccomyxa are fungi and marine animals, most importantly mussels. Moreover, there is a well-documented association between a Coccomyxa strain and Gingko biloba and some Coccomyxa-like microalgae have been found in the bark of other trees. Here we describe a green algal strain found in association with carnivorous plants of the genus Drosera L. The systematics of Coccomyxa based only on classical methods is problematic, due to the very simple morphology of the genus and its high phenotypic plasticity. Therefore, the microalga associated with Drosera plants was isolated, maintained in culture and subjected to an integrative taxonomy approach, including morphological, ultrastructural and molecular analyses, along with ecological considerations. Phylogenetic reconstructions based on the rbcL and 18S rRNA genes and molecular data obtained from the ITS2 spacer, including both sequence and secondary structure analyses, showed that the investigated microorganism belonged to a lineage distinct from those sequenced so far. An accurate taxonomic comparison between the microalga associated with Drosera and each of the species already described for the genus Coccomyxa was also carried out, considering morphology, ultrastructure and ecology. The results as a whole allowed us to erect a new species inside the genus Coccomyxa: Coccomyxa cimbrica K.Sciuto, B.Baldan & I.Moro