Systematik der Charophyceae

Zusammenfassung

Charophyceae are a class of macroscopic green algae exhibiting a complex whorlshaped thallus. They are closest related to the land plants. Their systematics is subjected to ongoing tuning based on integrative approaches combining morphology, anatomy, ontogeny, molecular phylogeny, and ecology. Charophyceae are member of the division Streptophyta (Charophyta) together with six other classes including the Embryophyceae, the real land plants. The conception of genera in Charophyceae is widely resolved comprising Chara, Lamprothamnium, Lychnothamnus, Nitellopsis, Nitella, and Tolypella. However, the conception of species is still under discussion searching for a compromise between the micro-species concept, established by A. Braun and W. Migula, and the macro-species concept suggested by R.D. Wood. Evaluating the European flora of Charophyceae, about 50 micro-species and just 20 macro-species exist. The currently used “pluralistic” conception based on assessment of interbreeding, phenology and ecological niches revealed about 40 species in Europe. Here, we summarise the current status of the systematics of the family Characeae. Selected gene sequence analyses were combined with diacritic morphological characteristics. Due to the high morphological variability the traditional species circumscription is not always consistent with genetic analyses. The applicability of the conceptions differed within the genera. Whereas the results in Nitella and Tolypella support the micro-species concept, in Chara the high morphological variability is not reflected by molecular phylogenetic analyses. However, because of the high potential of micro-species for ecological inferences a strict application of the macro-species conception would result in loss of valuable information.