March 1999, Volume 150, Issue 1, Pages 71 - 84

Original Paper

Phylogenetic Analysis of the SSU rRNA from Members of the Chrysophyceae Robert A Andersen 1,4 , Yves Van de Peer 2,5 , Daniel Potter 1,6 , Julianne P Sexton1 , Masanobu Kawachi 3,7 & Todd LaJeunesse 1,8 1Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, ME 04575, USA     2Department of Biochemistry, University of Antwerp (UIA), Universiteitsplein 1, B-2610 Antwerp, Belgium     3Marine Biotechnology Institute, 75-1 Dai-san chiwari Heita, Kamaishi City, Iwate 026 Japan     4Corresponding author; fax 1-207-633-9715 E-mail: Randersen@Bigelow.org 5Current address: Department of Evolutionary Biology, University of Konstanz, D-78457 Konstanz, Germany 6Current address: Department of Pomology, University of California, Davis, CA 95616, USA 7Current address: Microbial Culture Collection, National Institute for Environmental Studies, Tsukuba, Japan 8Current address: Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA

Keywords

18S rRNA;   chromophyte;   Chrysophyceae;   golden algae;   Synurophyceae;   taxonomy

Abstract

The nucleotide sequence for the nuclear-encoded small subunit ribosomal RNA gene (SSU rRNA) was determined for 24 species of the Chrysophyceae sensu stricto. These sequences were aligned, using primary and secondary structure, with nine previously published sequences for the Chrysophyceae, 14 for the Synurophyceae, and five for the Eustigmatophyceae (outgroup). Data analyses were the substitution rate calibration distance method using neighbor-joining (TREECON), Kimura 2-parameter neighbor-joining method (PAUP) and the maximum parsimony method (PAUP, PHYLIP). Trees from the analyses were largely congruent, but bootstrap support was weak at many nodes. The analyses recovered clades of uniflagellate and biflagellate organisms associated with current higher level taxonomy (e.g., subclass, order). The genus Ochromonas was polyphyletic, and O. tuberculata in particular was distantly related to the other Ochromonas species in the analysis. The family Paraphysomonadaceae occupied a basal position in three of four analyses. The class Synurophyceae appeared to be embedded within the Chrysophyceae, but bootstrap support was weak (< 50%) in all analyses except the PHYLIP parsimony analysis (= 81%). It was considered premature to place the Synurophyceae back into the Chrysophyceae based upon the analysis of one gene, especially given the ultrastructural and pigment differences between the two groups, but the relationship of these two groups deserves further study.

Received 8 January 1999; Accepted 7 February 1999

^© Macmillan Publishers Ltd 1999