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International Journal on Algae
SJR: 0.219 SNIP: 0.261 CiteScore™: 0.24

ISSN Imprimir: 1521-9429
ISSN On-line: 1940-4328

International Journal on Algae

DOI: 10.1615/InterJAlgae.v6.i3.10
pages 203-223

Estimation of taxonomic significance of certain taxonomic characters in unicellular green flagellate algae (Viridiplantae) invoking the data of genosystematics

N. P. Masyuk
N.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, 2, Tereshchenkovskaya St., 01001 Kiev, Ukraine

RESUMO

The paper deals with the morphological characters of unicellular green flagellate algae (GFA) associated with their photosynthetic apparatus (number, dimensions, localization, shape of plastids, structure of their external and internal surfaces, degree of their dissection and perforation, coloration, presence/absence of pyrenoids, their quantity, localization, shape, structure of the pyrenoid matrix and assimilation envelope). It has been shown that numerous parallelisms in distribution of different variants of these characters are observed at various levels of the phylogenetic tree of eukaryotes, which essentially restricts their application in the systematics of higher taxa. The attraction of other criteria (biochemical, molecular) to estimate the taxonomic significance of the mentioned characters confirms their low phylogenetic importance. The stable-inheritable morphological characters characterizing the photosynthetic apparatus are successfully used for diagnosis of species and intraspecific taxa. However, their use at the higher (superspecific) levels leads to the creation of artificial units convenient for practical work but not reflecting their relationships. The molecular data confirm their heterogeneity. There are no diagnostic characters outlining the groups of species within monophyletic clades at the molecular dendrograms. The clades recognized within Chlorophyceae by the molecular methods do not correspond to any traditional system. So, the taxonomic revision of traditional systems of unicellular green flagellate algae is untimely at present. First it is necessary to realize at least the following preliminary stages: (1) to elucidate the reasons for discrepancy between the phenotypic and genotypic systems at the lower taxonomic levels; (2) to work out the morphological and molecular standard of the species; (3) to reveal the diagnostic (phenotypic) characters which correlate phyletically with genotypic ones.