Transcript Invasive Species - School of Life Sciences

Objectives
Definitions
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
Definitions:
• 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.
Invasive species in Illinois:
Purple loosestrife Zebra mussel
Easter Island human population collapsed b/c
used up local resources + an invasive rat
immigrated (seed predator on major tree
species)
Vertebrates:
House Sparrow
• Competition from the House
Sparrow for cavity nests can
cause decline of some native
species.
• Introduced into
Brooklyn, New York,
in 1851.
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 Eating
Alligator
October 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
1. Arrival
2. Establishment
3. Spread
1. ARRIVAL:
Introduced deliberately:
Accidentally:
•naturalization societies •ballasts of ships
•Shakespeare fans
•unprocessed wood
•game animals
•fruit shipments
•domestic animals
•by-pass natural
barriers
1. Arrival: Vectors of invasion into ecosystems
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):
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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
Ballast Tanks
1. Arrival: Pathogens and Disease
“Forecast and control of epidemics in a globalized world.” Hufnagel et al. PNAS 2004
2. Establishment:
Characteristics of invasive species
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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.
Displacement or replacement?
• 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.
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)
34,000
Mammals (feral pigs, rats)
37,000
Birds (pigeons, starlings)
2,000
Fishes
1,000
Arthropods (ants, termites, other pests)
19,000
Mollusks (zebra mussel, asian clam)
1,200
Microbes (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
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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?