The taxonomic implications of genetic and environmentally induced variations in seaweed morphology

Morphological characters are the most widely used criteria for the discrimination of seaweed taxa. Even so, many examples of extreme phenotypic plasticity are known. Thus, several phycologists have recently initiated studies to evaluate the phenotypic range of taxa under varied conditions as well as to explore the degree of genetic control of individual characters. Several experimental techniques have been employed to enumerate the significance and basis of phenotypic plasticity in seaweeds, including culture studies, detailed seasonal observations of in situ populations, reciprocal transplantation of plants to diverse habitats, statistical analysis of character variations, and evaluation of genetic affinities. Obviously, the taxonomic status of seaweeds should reflect their genetic relationships. Three primary approaches are outlined including electrophoretic studies, quantitative genetic evaluations, and hybridization studies. A detailed summary of these genetic studies, as well as the other experimental field and laboratory techniques, is given in order to critically assess traditional taxonomic criteria and to aid in the search for new ones. An evaluation of the relative merits of morphological and biochemical characters in species delimitations is also outlined. It is suggested that there should be no tacit assumption that biochemical features are in some way more fundamental than morphological ones. Thus, even seemingly trivial morphological features may be of great adaptive value, even though not apparent to the taxonomist. A good taxonomic character is constant, readily observable, and the plant should survive identification. If obscure characters are used to delimit species, strenuous efforts should be made to correlate these characters with more readily observable ones. /// Morphologische Eigenschaften sind die meistgebrauchten Kriterien fur die Unterscheidung der benthischen Meeresalgen. Dennoch sind viele Beispiele von extrem phenotypischer Plastizität bekannt. Also haben einige Phycologen Studien begonnen, um die phenotypische Reichweite der Taxen unter verschiedenen Umstanden zu bestimmen, gleichfalls den Grad der genetischen Kontrolle der individuellen Eigenschaften zu erforschen. Verschiedene Versuchsmethoden wurden angewendet, um die Bedeutung und Basis der phenotypischen Plastizität von Meeresalgen aufzuzählen. Unter diesen waren Kulturstudien, detaillierte periodische Beobachtungen der in situ Populationen, gegenseitige Umpflanzung der P