1. 3.3 - How Introduced Species Affect Ecosystems Native species are plants and animals that naturally inhabit an area. Immigration to North America by people from other continents over the past 400 years has introduced many new species – some by accident, others on purpose. – These new species of plants, animals or microorganisms are called introduced species. Many of them are harmless or beneficial to their new environments. foreign species non-native species exotic species alien species Invasive species negatively impact native species (overtake their natural habitat / invade their bodies), and often reduce biodiversity as a result.

2. Plant & Animal Species Native Species Introduced beneficial benign Invasive harmful

3. An Example of a Beneficial Introduced Species The European leaf-eating beetle to the rescue! purple loosestrife was introduced to N. America from Europe (likely by accident via boats) in the early 1800s purple loosestrife quickly reproduces and destroys wetlands by choking out native plant species and by growing in clumps too dense to shelter wildlife after careful research, scientists determined that this species of beetle could safely be introduced into some of BC’s damaged wetland ecosystems to control the loosestrife population TASTY!

4. The Impact of Introduced Invasive Species Invasive species often… – have no natural predators – are aggressive competitors – reproduce fast

5. The Impact of Introduced Invasive Species Invasive species often take advantage of their new niche and can dramatically change an ecosystem through… 1.Competition…with native species for essential resources (food, habitat). The native species have an established balance that invasive species can throw off. 1.Predation: If the invasive species is a predator, it may have a larger impact on a prey population than native predators. The native prey species may not have adaptations to fight / escape.

6. The Impact of Introduced Invasive Species 3.Disease and Parasitism: by weakening certain species’ immune responses, a species invading an ecosystem has the opportunity to outcompete other species, drastically altering the entire ecosystem and the niches within it. Ex. Sea lampreys made their way from the Atlantic Ocean into the St. Lawrence Seaway via the canal system in the 1880s. Their vacuum-like mouths attach to fish & suck out their bodily fluids. Ex. Blister rust is a tree fungus (introduced in early 1900s) that attacks whitebark pine, weakening its defence mechanisms  it is more vulnerable to insect infestations. Controlled burns open spaces for new pines to grow. Slurp! The sea lamprey

7. The Impact of Introduced Invasive Species 4.Habitat Alteration: Some invasive species can change the physical structure / composition of an ecosystem by… digging / burrowing increasing soil erosion blocking sunlight decreasing dissolved O 2 in water changing soil chemistry upsetting balance of: – nutrient cycling – energy flow – pollination

8. Wild Boar one of the world’s most destructive invasive species roots, wallows & spreads weeds that interfere with succession eat native birds, frogs, reptiles, fruit, seeds, soil organisms,…

9. Invasive Species in British Columbia – Read p. 142

10. The Garry Oak Ecosystem – Under Siege Garry oak trees are a keystone species 95% of the original ecosystem has been lost to urban development, and the remaining 5% is threatened by invasive species. introduced invasive plant species: Scotch broom, English ivy & invasive grasses introduced invasive animal species: grey squirrel (larger & stronger than native red squirrels) & gypsy moth (strip Garry oaks of their leaves)

11. The Garry Oak Ecosystem – Under Siege It often takes human intervention to save established ecosystems. – The Garry Oak Ecosystem Recovery Team (GOERT) is trying to save several areas of the Garry Oak ecosystem in BC. – GOERT has representatives from many groups  the BC government, First Nations, conservationists, scientists and businesses. – Garry Oak forests are better adapted to summer droughts, therefore may be better suited to survive future climate change than Douglas fir forests.