ObjectivesDefinitions

Examples

Stages of Invasion

Arrival - how?

Establishment

What characteristics?

Spread

Why successful?

How impact native species?

Why are some ecosystems more vulnerable?

Control and Prevention

• Introduced (non-native, exotic) - species introduced deliberately or accidentally from somewhere else - more than 10,000 species in USA

• Domestic/Feral (released pets, livestock and game animals) - can spread disease, compete with native species

• Invasive species - species that spread subsequent to establishment usually at some cost.

Definitions:

Invasive species in Illinois:Purple loosestrife Zebra mussel

Easter Island human population collapsed b/c used up local resources + an invasive ratimmigrated (seed predator on major tree species)

• Introduced into Brooklyn, New York, in 1851.

Vertebrates:House Sparrow

• Competition from the House Sparrow for cavity nests can cause decline of some native species.

Insects:Africanized Bees

• In 1956, African Honey Bees were imported into Brazil

• In 1957, 26 African queens escaped

• Reached US in 1990

• More aggressive than European Honey Bees; have killed 1,000 people

• Impact honey and pollination industries

• Asian Long-horned Beetle– attacks and kills

many native trees

Found in Chicago in 1998

• Gypsy moth

• Introduced in 1860s

• Originally brought to the US for silk production

• now defoliates entire forests

Plants:Kudzu

• Introduced to U.S. in 1876 at the Philadelphia

Centennial Exposition

• promoted as a forage crop and ornamental plant until 1953

• kills other plants by smothering them under a solid blanket of leaves

•

Reptiles and Amphibians:

Cane toad – native to Central and South America

• Introduced world-wide to control insects (Australia)

• milky secretions are highly toxic. Kill dogs, cats and small native animals.

Python Explodes After EatingAlligatorOctober 5, 2005 MIAMI, (AP)

Alligators have clashed with nonnative pythons before in Everglades National Park. But when a 6-foot gator tangled with a 13-foot python recently, the result wasn’t pretty. The snake apparently tried to swallow the gator whole — and then exploded.

The gators have had to share their territory with a python population that has swelled over the past 20 years after owners dropped off pythons they no longer wanted in the Everglades. The Asian snakes have thrived in the wet, hot climate.

Gastropods: ZEBRA MUSSEL - Dreissena polymorpha

• Found in 1988 in Lake St. Clair (Lake between Huron and Erie, just off of Detroit, MI).

• Up to 70,000 individuals per m2

• Likely came to North America in ballast water

• One of the most expensive exotic species

• Restricts the flow of water through intake pipes (drinking, cooling, processing and irrigating water)

• Attaches to boat hulls, docks, locks, breakwaters and navigation aids, increasing maintenance costs and impeding waterborne transport.

Stages of invasion

3. Spread

2. Establishment

1. Arrival

1. ARRIVAL:

Introduced deliberately:

•naturalization societies

•Shakespeare fans

•game animals

•domestic animals

Accidentally:

•ballasts of ships

•unprocessed wood

•fruit shipments

•by-pass natural barriers

A. Intentional Release of Target Species

• Plants for Agriculture• Plants for Forestry• Plants for Soil Improvements

- fire suppression, erosion control• Ornamental Plants• Birds and Mammals for Hunting• Biological Control• Released Pets and Pet Trade

1. Arrival: Vectors of invasion into ecosystems

B. Release of Non-Target Species (“Accidental” Releases):

• Contaminants or Hitchhikers with Produce• Contaminants or Hitchhikers with Ornamental Plants• Contaminants or Hitchhikers with Aquaculture• Timber• Contaminants of Seed Stock• Cars• Planes• Hitchhikers with Packing Material, Cargo• Ballast in ships• Ship Hull Fouling• Tourists, Luggage• Canals

1. Arrival:Vectors of invasion into ecosystems

Ballast Tanks

“Forecast and control of epidemics in a globalized world.” Hufnagel et al. PNAS 2004

1. Arrival: Pathogens and Disease

2. Establishment: Characteristics of invasive species

• general diet and habitat requirements• high abundance• small body size• high reproductive potential (r-strategy)• good competitors• social / gregarious

(different characteristics may be important at different stages)

Generalities would be nice!Make invasion biology a predictive science.

3. Spread: Hypotheses for the success of introduced species:

• Escape from natural enemies predators, parasites, disease• Increased competitive ability outcompete native species• Pre-adapted to disturbed environments

3. Spread: How do they impact native species?

• Can be predators, competitors, parasites, diseases.

• Can modify habitat.

• Can promote spread of other invaders.

Ultimately…displace native species

Percentage of threatened or endangered species imperiled by:

• Habitat degradation and loss - 85%

• Invasive species - 49%

• Pollution - 24%

• Overexploitation - 17%

• Disease - 3%

Source: Wilcove et al.1998 BioScience

The Invasive Argentine ant

3. Spread: Invasive replaces native through time

Phrynosoma coronatum• Declining throughout its range.• A “sit and wait” ant specialist.• Doesn’t eat Argentine ant.

Mechanisms responsible for invasion success in Argentine ants:

• Escape from natural enemies: predators and parasites.• Pre-adapted to disturbed environments.• Different competitive environment - competitive release.• Increased competitive ability - increased density.

• Homogenization

“Process by which a mixture is made uniform throughout”.

• Biotic homogenization

Increasing similarity in species among areas.

• Habitat loss and modification coupled with the widespread introduction of a few species leads to homogenization.

Displacement or replacement?

•

3. Spread: What makes certain ecosystems vulnerable?

• Diverse, undisturbed ecosystems have few invaders “Biotic resistance”

• Disturbed habitats have more invaders

• Human residential areas: many European species that are commensal with humans

• Islands: little history with competitors, predators, parasites, or diseases

Over 2,000 species of birds have gone extinct on islands as a result of habitat loss and the introduction of predators and parasites.

Hawaii:

Habitat loss, malaria, rats and mongoose

Birds on islands (from Case 1996 Biol Con)

Estimated annual costs associated with non-native species:

Group costs (in millions)Plants (purple loosestrife, weeds) 34,000Mammals (feral pigs, rats) 37,000Birds (pigeons, starlings) 2,000Fishes 1,000Arthropods (ants, termites, other pests) 19,000Mollusks (zebra mussel, asian clam) 1,200Microbes (plant pathogens, animal disease) 41,000

All organisms over $136 billion per year

Source: Pimentel et al. 2000 BioScience

How do we control invasive species? • In urban and agricultural areas

pesticide/herbicide use still common

• Natural enemies - Biological Control

• Manage the landscape to minimize disturbance

Results of pesticide use

• Killed native competitors

• May select for resistance

• Health risks for people

Biological Control:• The use of one species to control another.• Usually a specialist predator or parasite of an invasive species.• Needs to be species-specific or can cause even worse problems.

Prevention

• Education is key• Research is still needed - generalities?• Monitoring programs - early detection• Prevent establishment - quarantine• Increased communication among agencies• Increase regulations

How can you stop the spread of exotics?

http://www.invasivespeciesinfo.gov/

Introduced Nile perch vs. native cichlid fish in Lake Victoria: how determine causation?

Observation: Cichlid fish populations declined after the introduction of Nile perch.

• Question: Did the introduction of the perch cause the decline in cichlid populations?

• Hypothesis 1: The introduction of Nile perch caused the decline of cichlid populations.

***Are there alternative hypotheses?

• H1: original hypothesis

• H2: A newly introduced cichlid parasite caused the decline.

• H3: A marked decline in aquatic vegetation on which cichlids feed caused the decline.

• H4: Dramatic changes in water chemistry caused by agricultural runoff caused the decline.

• H5….

• How do we determine causation?…

Meta-analysis of 63 studies:What is main conclusion about the ‘natural enemies hypothesis’ ?

Plant survival: with rabbits = 5%

without rabbits = 60%

Introduced Native

Effects of native vs. foreign mycorrhizal fungi on plant growth: What is the main conclusion?