|Komarek J, Steinmann P (1953)
Artaufspaltung bei Susswassertieren. [Species splitting in fresh-water animals.]
Schweiz Zeitschr Hydrol 15(2): 261-274
Abstract / NotesSome species are actively changing, forming ecotypes and geographical variations. Polytypy, such as occurs in the coregonids, is an indication of this process of active change. Polytypic variations are races as long as sexual union between the forms is a potential. New species are formed from races when such sexual union is no longer possible. The triclad, Planaria (Crenobia) alpina and its cluster of subspecies is discussed as a case in point. In the Mediterranean region there are three subspecies in addition to the typical form, C. alpina alpina. These vary in a constant fashion, but in most respects are identical to each other. From the Italian literature Komarek believes that Planaria (Dugesia) gonocephala is in the process of formation of a similar cluster of incipient, or actual species. A group of species of Fonticola, studied in the Balkan Peninsula, is also discussed, as are species of Neodendrocoelum. A simple case, the leeches Dina lineata and D. absoloni. is described in some detail. The former species is pigmented, has eyes, and is a surface dweller. The latter is albino and eyeless, and inhabits subterranean waters. The two have superimposed geographic ranges, and are identical to one another except in the two features mentioned. Komarek believes that the cave dweller arose from the surface dweller, not by the influence of the environment, but by the sudden appearance of a mutation, which could continue its existence only in subterranean waters where light was absent. A similar case, the cave salamander Proteus anguinus. is discussed.
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