Phylogenetic studies on Scenedesmaceae (Chlorophyta)

18S-RNA was analysed for 17 species from 8 genera of Scenedesmaceae sensu KOMAREK et FOTT (1983) and one strain of Coelastropsis (Coelastraceae) and Coelastrella (Scotiellaceae). According to the results a subfamily Desmodesmoideae was set up, the subgenera Acutodesmus and Scenedesmus were verified and Scenedesmus (Kermatia) pupukensis was transferred to Neodesmus. Dactylococcus dissociatus and the genus Tetradesmus were included in Acutodesmus. The two strains of Tetradesmus as well as the two strains of the varieties of S. pectinatus were not closely related and the placement of S. pectinatus var. pectinatus was not stable. It probably belongs to Enallax, while the other taxa belong to Acutodesmus, A strain labelled Schroederiella apiculata was recognised as a new species of Scenedesmus (S. hindakii). Scenedesmus acutiformis clustered separately and is preliminarily accepted as Enailax acutiformis. Pseudodidymocystis is a sister group to Desmodesmus. Dicloster was excluded from Scenedesmaceae and also from Chlorophyceae and is placed in Trebouxiophyceae. Coelastropsis costata has a 18S similar to Scenedesmus s.str., but is morphologically not closely related to that genus and is hence not transferred to Scenedesmus. The former Chlorella fusca var. vacuolatus (=Scenedesmus vacuolatus) is transferred to Coelastrella.