The genus Callitriche (water-starwort) in the Czech Republic. II. C. cophocarpa, C. stagnalis, C. platycarpa, C. xvigens

The second part of a complete revision of the genus Callitriche in the Czech Republic is presented. Four taxa are described in detail, and their ecological demands and distribution are discussed. Callitriche cophocarpa, probably the most abundant species of the genus, occurs in various types of standing and running waters from lowlands to mountains, except the extreme north of Bohemia, where it is possibly absent. Callitriche stagnalis most often grows in puddles on forest paths. It occurs nearly throughout the territory, but is surprisingly absent from South Moravia. Callitriche platycarpa has a markedly Subatlantic distribution. It is known from northern, northwestern and western Bohemia, forming the eastern border of its distribution. It inhabits a wide range of habitats, but the ecological optimum of this species is in streams with a muddy bottom. C. platycarpa is partially vicariant with C. cophocarpa, which has a rather Continental distribution. The hybrid C. ×vigens (C. cophocarpa × C. platycarpa) has been found in the Czech Republic for the first time. It can be found in areas where both parental species occur, and might be not so rare. However, it was also found in the Otava river, where C. platycarpa is not known to occur. Callitriche obtusangula, a species whose presence in the Czech Republic was reported to be probable according to some sources, has actually never been found in this country.