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DNA-Based Taxonomy in Ecologically Versatile Microalgae: A Re-Evaluation of the Species Concept within the Coccoid Green Algal Genus Coccomyxa (Trebouxiophyceae, Chlorophyta).

Malavasi V, Škaloud P, Rindi F, Tempesta S, Paoletti M, Pasqualetti M - PLoS ONE (2016)

Bottom Line: Our results are compared with those of a recent integrative study of Darienko and colleagues that reassessed the taxonomy of Coccomyxa, recognizing 7 species in the genus.We conclude that the 27-species scenario is presently the most realistic for Coccomyxa and we suggest that well-supported lineages distinguishable by ecological preferences should be recognized as different species in this genus.We also recommend that for microbial lineages in which the overall diversity is unknown and taxon sampling is sparse, as is often the case for green microalgae, the results of analyses for algorithmic DNA-based species delimitation should be interpreted with extreme caution.

View Article: PubMed Central - PubMed

Affiliation: Interdepartmental Center of Environmental Science and Engineering (CINSA), University of Cagliari, Cagliari, Italy.

ABSTRACT
Coccomyxa is a genus of unicellular green algae of the class Trebouxiophyceae, well known for its cosmopolitan distribution and great ecological amplitude. The taxonomy of this genus has long been problematic, due to reliance on badly-defined and environmentally variable morphological characters. In this study, based on the discovery of a new species from an extreme habitat, we reassess species circumscription in Coccomyxa, a unicellular genus of the class Trebouxiophyceae, using a combination of ecological and DNA sequence data (analyzed with three different methods of algorithmic species delineation). Our results are compared with those of a recent integrative study of Darienko and colleagues that reassessed the taxonomy of Coccomyxa, recognizing 7 species in the genus. Expanding the dataset from 43 to 61 sequences (SSU + ITS rDNA) resulted in a different delimitation, supporting the recognition of a higher number of species (24 to 27 depending on the analysis used, with the 27-species scenario receiving the strongest support). Among these, C. melkonianii sp. nov. is described from material isolated from a river highly polluted by heavy metals (Rio Irvi, Sardinia, Italy). Analyses performed on ecological characters detected a significant phylogenetic signal in six different characters. We conclude that the 27-species scenario is presently the most realistic for Coccomyxa and we suggest that well-supported lineages distinguishable by ecological preferences should be recognized as different species in this genus. We also recommend that for microbial lineages in which the overall diversity is unknown and taxon sampling is sparse, as is often the case for green microalgae, the results of analyses for algorithmic DNA-based species delimitation should be interpreted with extreme caution.

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The Rio Irvi river, Locality Montevecchio-Ingurtosu, Sardinia, Italy.A. The river base covered by iron sediments, B. The sampling site of Coccomyxa SCCA 048, C-D. Artificial colouring of the river water caused by high concentrations of Cd, Co, Zn and Fe heavy metals.
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pone.0151137.g001: The Rio Irvi river, Locality Montevecchio-Ingurtosu, Sardinia, Italy.A. The river base covered by iron sediments, B. The sampling site of Coccomyxa SCCA 048, C-D. Artificial colouring of the river water caused by high concentrations of Cd, Co, Zn and Fe heavy metals.

Mentions: A standard operating procedure that applies to the collection of the algae from freshwater and terrestrial habitats was used. The alga was found in a station (N 39.546894, E 8.480278) where pH of the water was 6.85. The collection was made by scraping reddish ferrous material from rocks present at the river's edge (Fig 1). The physico-chemical parameters measured in the station are given in Table 1.


DNA-Based Taxonomy in Ecologically Versatile Microalgae: A Re-Evaluation of the Species Concept within the Coccoid Green Algal Genus Coccomyxa (Trebouxiophyceae, Chlorophyta).

Malavasi V, Škaloud P, Rindi F, Tempesta S, Paoletti M, Pasqualetti M - PLoS ONE (2016)

The Rio Irvi river, Locality Montevecchio-Ingurtosu, Sardinia, Italy.A. The river base covered by iron sediments, B. The sampling site of Coccomyxa SCCA 048, C-D. Artificial colouring of the river water caused by high concentrations of Cd, Co, Zn and Fe heavy metals.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814044&req=5

pone.0151137.g001: The Rio Irvi river, Locality Montevecchio-Ingurtosu, Sardinia, Italy.A. The river base covered by iron sediments, B. The sampling site of Coccomyxa SCCA 048, C-D. Artificial colouring of the river water caused by high concentrations of Cd, Co, Zn and Fe heavy metals.
Mentions: A standard operating procedure that applies to the collection of the algae from freshwater and terrestrial habitats was used. The alga was found in a station (N 39.546894, E 8.480278) where pH of the water was 6.85. The collection was made by scraping reddish ferrous material from rocks present at the river's edge (Fig 1). The physico-chemical parameters measured in the station are given in Table 1.

Bottom Line: Our results are compared with those of a recent integrative study of Darienko and colleagues that reassessed the taxonomy of Coccomyxa, recognizing 7 species in the genus.We conclude that the 27-species scenario is presently the most realistic for Coccomyxa and we suggest that well-supported lineages distinguishable by ecological preferences should be recognized as different species in this genus.We also recommend that for microbial lineages in which the overall diversity is unknown and taxon sampling is sparse, as is often the case for green microalgae, the results of analyses for algorithmic DNA-based species delimitation should be interpreted with extreme caution.

View Article: PubMed Central - PubMed

Affiliation: Interdepartmental Center of Environmental Science and Engineering (CINSA), University of Cagliari, Cagliari, Italy.

ABSTRACT
Coccomyxa is a genus of unicellular green algae of the class Trebouxiophyceae, well known for its cosmopolitan distribution and great ecological amplitude. The taxonomy of this genus has long been problematic, due to reliance on badly-defined and environmentally variable morphological characters. In this study, based on the discovery of a new species from an extreme habitat, we reassess species circumscription in Coccomyxa, a unicellular genus of the class Trebouxiophyceae, using a combination of ecological and DNA sequence data (analyzed with three different methods of algorithmic species delineation). Our results are compared with those of a recent integrative study of Darienko and colleagues that reassessed the taxonomy of Coccomyxa, recognizing 7 species in the genus. Expanding the dataset from 43 to 61 sequences (SSU + ITS rDNA) resulted in a different delimitation, supporting the recognition of a higher number of species (24 to 27 depending on the analysis used, with the 27-species scenario receiving the strongest support). Among these, C. melkonianii sp. nov. is described from material isolated from a river highly polluted by heavy metals (Rio Irvi, Sardinia, Italy). Analyses performed on ecological characters detected a significant phylogenetic signal in six different characters. We conclude that the 27-species scenario is presently the most realistic for Coccomyxa and we suggest that well-supported lineages distinguishable by ecological preferences should be recognized as different species in this genus. We also recommend that for microbial lineages in which the overall diversity is unknown and taxon sampling is sparse, as is often the case for green microalgae, the results of analyses for algorithmic DNA-based species delimitation should be interpreted with extreme caution.

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