, Volume 241, Issue 3-4, pp 185-191
Date: 04 Nov 2003

Phylogenetic relationships of Scenedesmus and Acutodesmus (Chlorophyta, Chlorophyceae) as inferred from 18S rDNA and ITS-2 sequence comparisons

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The complete 18S rDNA and ITS-2 sequences of two strains of Scenedesmus arcuatus were determined and subjected to phylogenetic analyses. Furthermore, ITS-2 sequences of Scenedesmus obtusus, of S. hindakii, and of Acutodesmus regularis were investigated. Phylogenetic analyses indicated that S. hindakii is most closely related to S. raciborskii and/or S. obtusus, embedded in the Scenedesmuscluster. The morphologically similar S. arcuatus and its variety platydiscus branched outside the Scenedesmus/Acutodesmus cluster (18S) or together with A. regularis and A. pectinatus (ITS-2). Therefore, the genera Acutodesmus and/or Scenedesmus are paraphyletic. S. arcuatus is not closely related to S. hindakii.

We thank Dipl. Biol. Anke Braband and Dr. R. Hiesel (both Berlin, Germany) for sequencing, Mrs. Gertrud Popowytsch (Jülich, Germany) for preparing Fig. 3, Mrs. Janet Carter-Sigglow, MA, for proofreading the English, and Dr. P. Tsarenko for helpful comments on the manuscript.