Original paper
Towards a taxonomic revision of the genus Scytonema: morphological, biochemical and molecular approaches
Hoffmann, Lucien; Asencio, Antonia D.; Schmit, Claudine
Algological Studies/Archiv für Hydrobiologie, Supplement Volumes No. 94 (1999), p. 173 - 174
published: Sep 16, 1999
DOI: 10.1127/algol_stud/94/1999/173
ArtNo. ESP142012900013, Price: 29.00 €
Abstract
The taxonomy of blue-green algae faces many problems. Many cytomorphological, ecophysiological, biochemical, genetic data accumulate on isolated strains, but only rarely are the different approaches applied to a larger set of strains or the results used in order to revise the existing classification of blue-green algae, so that the progress in the re-evaluation of the present classification system is very slow. In addition, in many experimental works, the specific or generic names applied to the strains are often arbitrarily used and no description or illustration is generally given so that it is often impossible to use these data for taxonomic purposes. This for example often leads to incongruent phylogenetic trees, simply because the strains are partly misidentified. The ecologist who works with natural populations, however, needs to distinguish morphologically and ecologically stable types. It seems thus important to study blue-green algae by classical botanical methods and to test with molecular approaches whether the types which are recognised on the basis of their morphology and ecology really represent distinct taxonomic units. This approach is used for revising the genus Scytonema. The false-branching, heterocystous genus Scytonema is widespread in aerophytic habitats, especially in tropical regions. The taxonomy of the genus is studied following a polyphasic approach, by using a combination of features ranging from classical botanical methods to molecular biology (Fig. 1). The morphology (thallus morphology, trichome structure, cell morphology and dimensions, type of branchings, characteristics of the sheath,. .. ) and development pattern of hormogonia of about 60 clonal strains isolated from various terrestrial habitats from different parts of the world (Europe, South America, Southeast Asia, Australia, Africa) are studied in parallel to the characteristics of the collected herbarium material. The biochemical parameters studied in the clonal cultures are the phycobiliproteins (presence of phycoerythrin/phycoerythrocyanin in addition to phycocyanin), the carotenoid composition, as well as the presence of ultraviolet-absorbing scytonemin and mycosporine-like compounds. The molecular technique 'Amplified Ribosomal DNA Restriction Analysis' (ARDRA) is applied to the isolated strains in order to test the genetic relatedness of taxa grouped together on the basis of the morphological and biochemical features.
Keywords
Cyanophyceae • Cyanobacteria • Scytonema • taxonomy