| Heterotrophic Protists and he Origins of Photosynthetic Eukaryotes: An Updated Summary
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| Charles J. O'Kelly
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Bigelow Laboratory for Ocean Sciences, McKown Point, West Boothbay Harbor
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| ABSTRACT |
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The eukaryotic algae is a polyphyletic assemblage of organisms. Only some algae may be called plants if this word is to have a phylogenetic meaning. Therefore, a proper understanding of algal systematics and phylogeny must depend on understanding the relationships of alga groups with other eukaryotes, particularly other protists. A speculative phylogeny is presented in which mitochondrial eukaryotes are divided into three clades on the basis of mitochondrial cristae architecture. Structural features of jakobid flagellates, treated as stem taxa for the three clades, support this idea. Euglenoids-belong to the clade marked by the presence of discoidal mitochondrial cristae, and are considered to be the sister taxa of kinetoplastid flagellates (bodonids and trypanosomes). Golden algae, prymnesiophytes chlorarachniophytes and dinoflagellates belong to the clade marked by tubular mitochondrial cristae. Golden algae belong to a larger stramenopile or heterokont group and may be sister taxa to bicosoecid flagellates, while dinoflagellates belong to an alveolate clade that also includes ciliates and apicomplexans. The likely sister taxa of chlorarachniophytes and prymnesiophytes have not been identifies. Cryptomonads, green algae, red algae and glaucocystophytes belong to the clade marked by flattended mitochondrial cristae, as do the true fungi and animals. The aplastidic protist Goniomonas is the likely sister taxon of the photosynthetic cryptomonads, but relationships among the taxa are otherwise poorly understood.
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| Key words:
algal evolution, taxonomy, phylogeny, jakobid flagellates mitochondrial structure |
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