ABSTRACT
The geohistoric evolution and actual climatic zone arrangement of the Earth’s surface determine the floral and faunal patterns that have evolved as a result of a natural process, under natural conditions. A good example is provided by the silver crucian carp, which is a competitor of the crucian carp, the tench and the common carp. The silver crucian carp not only displaces the tench and the crucian carp from their habitat but, through its intensive sexual-parasitic mode of reproduction, it also influences the spawning success of species occupying some other feeding niches. The original home of the silver crucian carp is Southeast Asia, but the fish species occurs in the overwhelming majority of the European countries. In north-eastern China, the silver crucian carp was considered to be triploid, as the chromosomal number in somatic cells is 156 and the population propagates by gynogenesis.
