title: Origin and evolution of the colonial volvocales (Chlorophyceae) as inferred from multiple, chloroplast gene sequences.
abstract: A combined data set of DNA sequences (6021 bp) from five protein-coding genes of the chloroplast genome (rbcL, atpB, psaA, psaB, and psbC genes) were analyzed for 42 strains representing 30 species of the colonial Volvocales (Volvox and its relatives) and 5 related species of green algae to deduce robust phylogenetic relationships within the colonial green flagellates. The 4-celled family Tetrabaenaceae was robustly resolved as the most basal group within the colonial Volvocales. The sequence data also suggested that all five volvocacean genera with 32 or more cells in a vegetative colony (all four of the anisogamous/oogamous genera, Eudorina, Platydorina, Pleodorina, and Volvox, plus the isogamous genus Yamagishiella) constituted a large monophyletic group, in which 2 Pleodorina species were positioned distally to 3 species of Volvox. Therefore, most of the evolution of the colonial Volvocales appears to constitute a gradual progression in colonial complexity and in types of sexual reproduction, as in the traditional volvocine lineage hypothesis, although reverse evolution must be considered for the origin of certain species of Pleodorina. Data presented here also provide robust support for a monophyletic family Goniaceae consisting of two genera: Gonium and Astrephomene.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. nozaki@biol.s.u-tokyo.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Nozaki
authors.forename: K
authors.initials: K
authors.lastname: Misawa
authors.forename: T
authors.initials: T
authors.lastname: Kajita
authors.forename: M
authors.initials: M
authors.lastname: Kato
authors.forename: S
authors.initials: S
authors.lastname: Nohara
authors.forename: M M
authors.initials: MM
authors.lastname: Watanabe
mesh_terms: D020418:Algal Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D000460:Chlorophyta / Q000145:classification / Q000235:genetics*; D018742:DNA, Chloroplast / Q000737:chemistry / Q000235:genetics*; D021901:DNA, Intergenic / Q000235:genetics; D019143:Evolution, Molecular; D007438:Introns / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D045331:Photosystem I Protein Complex; D010802:Phylogeny; D017354:Point Mutation; D006180:Proton-Translocating ATPases / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D020418:Algal Proteins; D001426:Bacterial Proteins; D018742:DNA, Chloroplast; D021901:DNA, Intergenic; D008565:Membrane Proteins; C073973:PSI-A protein, Synechococcus; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; C089909:photosystem I, psaB subunit; D006180:Proton-Translocating ATPases; D012273:Ribulose-Bisphosphate Carboxylase