ABSTRACT
For millions of years geographical features have provided environmental barriers that have given rise to isolated ecosystems essential for species to evolve. With the advent of humans, these natural barriers to the migration of species, which previously resulted in such a wealth of biodiversity, have been rendered ineff ective by the gradual ‘opening up’ of the globe. This process has resulted in species being moved outside of the native range and introduced into new areas. Sometimes these species have become established and thrived, and can have considerable impact on the invaded environment.
