Invasive Species
What are native species?
Native species are those that normally live and thrive in a particular community.
They occupy specific habitats and have specific niches in their native environment.
They have natural predators that help to keep their populations in check.
Buffalo Grass
Scissor tailed Flycatcher
Black Bear
Definition
• Invasive species-are plants, animals, or pathogens that are non-native
to the ecosystem under consideration and whose introduction causes
or is likely to cause harm.
How did they get here?
• Some introduced deliberately:
• Some accidental:
• naturalization societies
• ballasts of ships
• Shakespeare fans
• unprocessed wood
• game animals
• fruit shipments
• domestic animals
• by-pass natural barriers
What makes certain ecosystems more
vulnerable?
Diverse, undisturbed communities have few invaders
Disturbed habitats: full of invaders
Human residential areas: many European species
that are commensal with humans
Islands: little history with competitors, predators,
parasites, or diseases
Common characteristics of invasive species
Invasive species in general:
• Have few natural
predators, competitors,
parasites or diseases
• Have high reproductive
rates
• Are long-lived
• Are generalists
• Are pioneer species
Characteristics that make Zebra mussels a good
invader include its ability to tolerate a widerange of environments, and high reproduction
rate; female mussels release up to 100,000 eggs
ability to tolerate a wide-range of environments
year.
Discussion: how would these characteristics enable a species to become invasive?
What traits are common to invasive plant
species
Characteristics that make tree-of-heaven a good
invader include its ability to flower early (within
2 years), ability to spread asexually, and fast
growth rate.
• Self-compatible
• Flower early
• Produces abundant seed
• Disperse seed widely
• Grow rapidly
• Spread asexually
• Strong competitors
Impacts of invasive species
Economic impacts:
Invasive species are responsible for tremendous
economic losses through loss in forest and agricultural
productivity, spread of diseases that impact humans,
among other impacts.
European starlings, Sturnus vulgaris, spread
diseases to wildlife, livestock, and humans,
damage agricultural crops, and displace
native birds. Their damage to agricultural
crops is estimated at $800 million annually.
European Starling
•First successful introduction was 60 European
starlings released in Central Park, NY. in 1890, by
fans of Shakespeare
–competes with
bluebirds,
woodpeckers
Do we have any?
• Zebra mussel
• What: Mollusk
• How: Caspian Sea region of Asia; accidentally released into Lake St. Clair in
1988 in ship ballast water
• How Bad: Voracious filter feeders that out-compete native animals; fouls
boats & clogs intake pipes at power plants and municipal water sources
Do we have any?
• Dutch Elm Disease
• What: Fungus
• How: Asia; one strain of the disease arrived in the 1930s in Cleveland, OH on
infected elm logs from Europe; a more virulent strain arrived in 1940s
• How Bad: Elms were once the nation’s most popular urban street tree, have
now largely disappeared from both urban and forested landscapes. It is
estimated that “Dutch” elm disease has killed over 100 million trees.
Do we have any?
• Fire Ant
• What: Insect
• How: South America; accidentally introduced to Alabama in 1930s
• How Bad: Aggressive, multiple biter with painful venom and chance of allergy;
may also damage fruits, berries and young crops; also damage electric boxes;
ant mounds are a hazard to farm equipment.
Do we have any?
• Musk Thistle
• What: Weed
• How: Europe and Eurasia; Introduced to OK in 1944 possibly in contaminated
seed
• How Bad: Hardy weed that outcompetes native vegetation
HUGE PROBLEMS
• https://www.youtube.com/watch?v=rPeg1tbBt0A (Asian Carp)
• https://www.youtube.com/watch?v=Gtqb41CjQfc (Zebra Mussels)