The place and role of organisms in nature is the result of a long evolutional process, which had as result the integrity of ecosystems. The geographic distribution of species is determined by abiotic (environmental factors, geophysical barriers etc.) and biotic (interspecific relations) factors. In consequence a species will enlarge its area as far as abiotic and biotic factors will allow (Eber&Brandl 1997).
One of the side effects of the socio-economic globalization process is the voluntary or involuntary translocation of organisms by humans and the changing of natural barriers. Although introduction of species is not a new phenomenon, the recognition of the impact of these species on native organisms is just started (Lodge 1993).. The initial lack of interest may be explained by the fact, that most of non-native species do not cause spectacular environmental changes or ecological catastrophes (Williamson & Fitter 1996). However, today invasive species and introduction of species are one of the top issues of the scientific world. | 
