The introduction of non-native plant and animal species can often cause a lot of problems for native populations:
Plants:
For plants, exotic species often become invasive and destroy habitats by out competing through crowding and superior recruitment. In successive generations, the introduced species will dominate the landscape over species that may have inferior foraging and nesting characteristics. Also, the introduced species will not have the specific attributes that the native species have adapted in conjunction with their native pollinators over time.
Animals:
The introduction of non-native animal species can have detrimental effects in the form of direct foraging competition, competition for nesting sites, and also the possibility that the introduced species may become predator of the native population.
CASE STUDY
Alliara petiolata; The plant that is a double threat to the West Virginia white butterfly
The Victim: The West Virginia White Butterfly
The Perpetrator: The Garlic Mustard Plant
The issue:
The West Virginia white butterfly has a specific link with a native plant species from the mustard family known as “toothwort”. This plant is the only host species for the caterpillar and has recently come under threat by the garlic mustard plant(Alliaria petiolata). Once introduced to an area, garlic mustard out competes native plants by aggressively monopolizing light, moisture, nutrients, soil, and space. In some areas, the garlic mustard plant has totally out competed the toothwort to the level of local extinction.
In addition to the fact that this plant is invasive, there are other physical properties of the plant that make it a much bigger threat. The garlic mustard plant also contains a chemical which has a toxic effect on the West Virginia butterfly’s eggs, causing their death.
Additional Issues:
The garlic mustard plant has also effected other native spring wildflowers like spring beauty (Claytonia virginica), wild ginger (Asarum canadense), bloodroot (Sanguinaria canadenesis), and trilliums (Trillium species). Two other native butterfly species, the falcate orange-tip (Anthocharis midea annicka) and the mustard white butterfly (Pieris oleracea), are also at risk when garlic mustard replaces their host plants.