How Introduced Species Affect Ecosystems Chapter 3.3

Some Terms Native species: plants and animals that naturally inhabit an area. Introduced (foreign) species: a species that is not native to the area and has been introduced (usually) by humans, accidently or intentionally.

Invasive Species Many introduced species help or at least do not harm the ecosystem they come to. However, some take over the habitat of the native species. These are called invasive species. Invasive species often have high reproduction rates, are aggressive competitors, and lack natural predators.

Invasive Species Purple Loosestrife

Invasive Species Eurasian Milfoil

Invasive Species The aquatic weevil (native in BC) is a natural control for milfoil (it eats it). The challenge is getting it in our lakes.

Invasive Species American Bullfrog

Invasive Species European Starling

The Starling Outcompetes the Western Bluebird for Nesting Sites

4 Ways Invasive Species Can Be Harmful 1) Competition - compete against native species for resources (food, habitat) Ex: Florida wasp became extinct a few years after the southeast Asian wasp became established.

4 Ways Invasive Species Can Be Harmful 2) Predation - introduced predators can have a BIGGER impact on prey than native predators. In New Zealand, European rats have caused the extinction of 9 species of birds.

Why are Introduced Predators Different? Predator-prey relationships develop over thousands of years Native species have no defenses and may be consumed to the point of extinction is a short time The loss of the native species can throw the whole ecosystem (food chain) out of balance

4 Ways Invasive Species Can Be Harmful 3) Disease/ Parasites - invasion of parasites and disease can weaken immune response of native species. Parasitic lamprey sucks the fluids from other fish.

Disease/ Parasites Many Hawaiian birds became extinct after falling victim to malaria, brought by the introduced Asian songbird. I’iwi bird, endemic to the Hawaiian Islands is endangered.

4 Ways Invasive Species Can Be Harmful 4) Habitat Alteration - when an invasive species makes a habitat unsuitable for native species. On Haida Gwaii (Queen Charlotte Islands), introduced deer have changed the ecosystem

Habitat Alteration Island with deerIsland without deer

Habitat Alteration What are some other ways that invasive species can alter habitats? – Change in light levels – Change in dissolved oxygen (water) – Change in soil chemistry – Upset the nutrient cycle balance