Introduced species
Introduced species are those that have been moved intentionally or unintentionally by humans into a new geographic location where they are not naturally found.
Some may become established in this new location and are then termed naturalised species.
Some of these naturalised species can spread rapidly and outcompete or prey on native species - these are termed invasive species.
Invasive species can eliminate native species therefore reducing species diversity.
They may spread rapidly because this new location is free of predators, parasites and competitors that would normally limit their population in their natural environment. Invasive species can have a severe negative effect on the biodiversity in an ecosystem.