Abstract.
The chloroplasts of euglenophytes and dinoflagellates have been suggested to be the vestiges of endosymbiotic algae acquired during the process of evolution. However, the evolutionary positions of these organisms are still inconclusive, and they have been tentatively classified as both algae and protozoa. A representative gene of the mitochondrial genome, cytochrome oxidase subunit I (coxI), was chosen and sequenced to clarify the phylogenetic positions of four dinoflagellates, two euglenophytes and one apicomplexan protist. This is the first report of mitochondrial DNA sequences for dinoflagellates and euglenophytes. Our COXI tree shows clearly that dinoflagellates are closely linked to apicomplexan parasites but not with algae. Euglenophytes and algae appear to be only remotely related, with euglenophytes sharing a possible evolutionary link with kinetoplastids. The COXI tree is in general agreement with the tree based on the nuclear encoded small subunit of ribosomal RNA (SSU rRNA) genes, but conflicts with that based on plastid genes. These results support the interpretation that chloroplasts present in euglenophytes and dinoflagellates were captured from algae through endosymbioses, while their mitochondria were inherited from the host cell. We suggest that dinoflagellates and euglenophytes were originally heterotrophic protists and that their chloroplasts are remnants of endosymbiotic algae.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received: 24 March 1997 / Accepted: 21 April 1997
Rights and permissions
About this article
Cite this article
Inagaki, Y., Hayashi-Ishimaru, Y., Ehara, M. et al. Algae or Protozoa: Phylogenetic Position of Euglenophytes and Dinoflagellates as Inferred from Mitochondrial Sequences. J Mol Evol 45, 295–300 (1997). https://doi.org/10.1007/PL00006233
Issue Date:
DOI: https://doi.org/10.1007/PL00006233