Native and Non Native species

Native Species

•         species naturally found in particular ecosystems

•         well adapted to the conditions of the ecosystem

•         population kept in balance by abiotic & biotic factors that limit its growth

 

Non-Native Species

•         a.k.a. introduced or alien species

•         sometimes considered invasive species

•         species introduced into an ecosystem that evolved in and are adapted to a foreign ecosystem

 

Methods of Introduction

Accidental •stowaways in ships and airplanes •shoe soles, clothing, luggage, bodies of travelers •parasites, insects on shipped plants, lumber, animals •storm winds

Deliberate •as pets •as game or fish stock •imported ornamental plants for landscaping •to establish agriculture or livestock •to control the population of another species

 

Impact

Little to None: 90%

•         non-native cannot thrive in new environment and eventually dies out

OR

•         non-native fits in well with native species, thrives, but causes no harm

Significant: 10%

•non-native becomes invasive, lacking limits to its growth

•outcompetes native species for resources (space, food, water), causing their decline

•becomes difficult to impossible to limit or remove from ecosystem

 

Case Study:   Spotted Knapweed

• Accidentally introduced mixed with imported alfalfa seed from Europe early 1900’s

•         Secretes toxins to inhibit growth of neighboring native grasses

•         Spread over billions of acres of rangeland in US & Canada

•         Bitter & inedible to native herbivores

•         Endangering elk, ruining cattle grazing land

•         Control efforts unsuccessful

 

Case Study:   Zebra Mussel

•         Accidentally introduced into the Great Lakes by European ships discharging ballast water in 1988

•         Have spread throughout the lakes, Mississippi River, into several states and Canada

•         Outcompete native filter feeders, displacing native mussels and diminishing populations of invertebrates and fishes whose larvae depend on plankton 

•         Clog intake pipes, accumulate on boat hulls

•         Some ducks eat them, but not enough

•         programs to educate boaters to minimize spread

•         not under control

Case Study:  Rabbits in Australia

•         Introduced deliberately for sport shooting in 1859

• No native carnivores ate the rabbits to control their population

• Rabbits exploded, overgrazing areas that supported kangaroo & domestic sheep

• Foxes introduced to control rabbits, but found other mammals easier to catch

• Virus introduced to kill rabbits, they became resistant and exploded again

• Second virus introduced succeeded in killing 95%, allowing regrowth of plants

•         Remember!

• In their native environments they fit in, are kept in balance, and don’t cause destruction. 

• They only become problems when they enter a foreign ecosystem that they didn’t evolve to be a part of. 

•         There are roughly 7,000 non-native species in the United States

•  Only 10% have become invasive