Abstract
Compared to other mating groups of the Closterium ehrenbergii species complex distributed in subtropical to warm temperate regions, such as Groups A, B, and H, members of Group P have remarkably large cells and show high polyploidy. Ecologically, they are unusual in occurring in cold running waters; most desmids are found in warm stagnant waters. Members of Group P occur in a vast area of the Northern Hemisphere. Strains from Japan, Europe, and the United States are all sexually compatible with one another and the zygospores obtained in all test crosses produced viable offspring, although considerably lower F1 viability was observed in certain crosses involving strains with deleterious genetic factors. Two complementary mating types commonly coexisted at the localities sampled in Denmark, France, and England, but no site in Japan was found to have two coexisting mating types. All Japanese samples studied contained vegetative cells of only one mating type, either plus or minus. The nature of species in freshwater algae of worldwide distribution is discussed.
Published Version
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