Taxonomic revision of oil-producing green algae, Chlorococcum oleofaciens (Volvocales, Chlorophyceae), and its relatives

Historically, species in Volvocales were classified based primarily on morphology. Although the taxonomy of Chlamydomonas has been re‐examined using a polyphasic approach including molecular phylogeny, that of Chlorococcum (Cc.), the largest coccoid genus in Volvocales, has yet to be reexamined. Six...

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Published in:Journal of phycology Vol. 51; no. 5; pp. 1000 - 1016
Main Authors: Kawasaki, Yuriko, Nakada, Takashi, Tomita, Masaru
Format: Journal Article
Language:English
Published: United States Blackwell Publishing Ltd 01-10-2015
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Summary:Historically, species in Volvocales were classified based primarily on morphology. Although the taxonomy of Chlamydomonas has been re‐examined using a polyphasic approach including molecular phylogeny, that of Chlorococcum (Cc.), the largest coccoid genus in Volvocales, has yet to be reexamined. Six species thought to be synonymous with the oil‐producing alga Cc. oleofaciens were previously not confirmed by molecular phylogeny. In this study, seven authentic strains of Cc. oleofaciens and its putative synonyms, along with 11 relatives, were examined based on the phylogeny of the 18S ribosomal RNA (rRNA) gene, comparisons of secondary structures of internal transcribed spacer 1 (ITS1) and ITS2 rDNA, and morphological observations by light microscopy. Seven 18S rRNA types were recognized among these strains and three were distantly related to Cc. oleofaciens. Comparisons of ITS rDNA structures suggested possible separation of the remaining four types into different species. Shapes of vegetative cells, thickness of the cell walls in old cultures, the size of cells in old cultures, and stigma morphology of zoospores also supported the 18S rRNA grouping. Based on these results, the 18 strains examined were reclassified into seven species. Among the putative synonyms, synonymy of Cc. oleofaciens, Cc. croceum, and Cc. granulosum was confirmed, and Cc. microstigmatum, Cc. rugosum, Cc. aquaticum, and Cc. nivale were distinguished from Cc. oleofaciens. Furthermore, another related strain is described as a new species, Macrochloris rubrioleum sp. nov.
Bibliography:ArticleID:JPY12343
Figure S1. Permanent preparation of Macrochloris rubrioleum Yur. Kawas. & Nakada sp. nov. (TNS-AL-58908; holotype).Appendix S1. Alignment used in the 18S rRNA gene phylogenetic analyses in NEXUS format.Appendix S2. Alignment used in the phylogenetic analyses of ITS rDNA region in NEXUS format.
Yamagata Prefectural Government and Tsuruoka City
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ObjectType-Article-1
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content type line 23
ISSN:0022-3646
1529-8817
DOI:10.1111/jpy.12343