Invasive Species
Lecture Objectives:
1. Be introduced to biological invasions
2. Know several examples of invasive
species
3. Learn what you can do to stop the
spread of invasive species
Definitions:
Introduced (non-native, exotic)
- species introduced deliberately or accidentally from
somewhere else
Domestic/Feral (released pets, livestock and game animals)
- can spread disease, compete with native species
Human commensal or subsidized (out of control natives)
- native species that benefit from our land use
(disturbance)
Invasive species
- species that spread subsequent to establishment
usually at some cost.
Invasive Species
Some introduced
deliberately:
•naturalization
societies
Some accidental:
•ballasts of ships
•unprocessed wood
•Shakespeare fans
•fruit shipments
•game animals
•domestic animals
•by-pass natural
barriers
Vectors of invasion into ecosystems
Intentional Release of Target Species into Containment:
- Escapes from Zoos and Botanical Gardens
- Farmed Species
- Aquaculture
- Research
Vectors of invasion into ecosystems
Intentional Release of Target Species into the Environment:
- 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
Vectors of invasion into ecosystems
Release of Non-Target Species (AKA “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
Hull Fouling
Tourists, Luggage
Canals
Ballast Tanks
Movement of/ increased exposure to exotic
species includes pathogens!!
•
Emerging Infectious Disease – never known
before or absent for 20 years
•
Schistosomiasis, AIDS, SARS, etc.
“Forecast and control of epidemics in a globalized world.” Hufnagel et al. PNAS 2004
• In 1999, there were more than 50,000 exotic
species in the USA
Why study biological invasions?
Consequences
threaten biodiversity
costly
widespread
Unique opportunities for basic research
community ecology
animal behavior
evolution
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
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
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
Characteristics of invasive species
general diet and habitat requirements
high abundance
small body size
high reproductive potential (r-strategy)
good competitors
social / gregarious
Generalities would be nice!
Make invasion biology a more predictive science.
Stages of invasion
1. Opportunity (transport)
2. Establishment
3. Spread
(different characteristics may be important at different stages)
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
Birds
Mute swan
European starling
Monk Parakeet
European Starling
•First successful introduction was 60 European
starlings released in Central Park, NY. in 1890, by
fans of Shakespeare
–competes with
bluebirds,
woodpeckers
•slippery sidewalks
House Sparrow
•Competition from the House
Sparrow for cavity nests can
cause decline of some native
species.
•The House Sparrow
was 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
Insects
• Crop pests
– boll weevil, corn
borer
Adult boll weevil
• Culex mosquitos
– carry avian malaria
and pox
– driven 20 Hawaiian
bird species extinct
Insects
• Asian Long-horned
Beetle
– attacks and kills
many native trees
Found in Chicago in 1998
Insects
• Gypsy moth
•Introduced in
1860s
•Originally
brought to the US
for silk production
•now defoliates
entire forests
Reptiles and Amphibians
Cane toad – native to Central and South America
•Introduced world-wide to
control insects
•milky secretions are highly
toxic. Kill dogs, cats and
small native animals
Reptiles and Amphibians
Brown Tree Snake
•Introduced to Guam via cargo
transported by U.S. military
ships during World War II
•On Guam wiped out 9
of 13 indigenous bird
species
Mammals
• Goats and pigs
– in Hawaii wiped out
native plants
• Horses in Grand Canyon
– causing erosion
• Game animals
– “Texotics”
“Texotics” Oryx
Photo: Dr Mike Hill
Plants
Kudzu
•Introduced into the U.S.
in 1876 at the
Philadelphia Centennial
Exposition
•promoted as a forage crop and an ornamental plant
until 1953
•kills other plants by smothering them under a solid
blanket of leaves
Plants
Garlic mustard
•poses a severe threat to native plants and animals
•garlic mustard
outcompetes native plants
by monopolizing light,
moisture, nutrients, soil and
space.
•Not as good food
for herbivores as
many native species
Buckthorn
Fish
Northern Snakehead
(Channa argus)
Found in Maryland in 2002
Giant snakehead (Channa
micropeltes) found in Wisconsin in
2003
www1.ncdc.noaa.gov/pub/data/images/ great-lakes-ice-avhrr.gi
Laurentian Great Lakes
Mills et al. 1993
Over 140 exotic species
Many fish species
were (and continue to
be) released
intentionally
Erie
Many other exotics have entered the lake
accidentally:
Canals
Escape from captivity
Ballast water
Bait buckets, live wells and gear
19 locks, filled and emptied by gravity
Welland Canal
Niagara Falls was the
major obstacle to an
uninterrupted waterway
Begun in 1829
Sea Lamprey
(Petromyzon marinus)
Invaded the Great Lakes after the opening of
the Welland Canal
Devastated native fish stocks, especially lake trout
Other fish (>25 species)
Alewife (1873)
(Alosa pseudoharengus)
Canals
Coho salmon (1933)
(Oncorhynchus kisutch)
Deliberate release
Round goby (1990)
(Neogobius melanostomus)
Ballast water
Chinook salmon (1873)
(Oncorhynchuys tshawytscha)
Deliberate release
Exotic Crustaceans (>6 species)
Bythotrephes cederstromi (1984)
Ballast water
Cercopagis pengoi (1998)
Ballast water
Exotic mollusks (> 14 species)
Asiatic clam (1980)
(Corbicula fluminea)
Aquarium release
Quagga mussel (1990s)
(Dreissena bugensis)
Ballast water
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
Will biofoul and restrict the flow of water through
intake pipes (drinking, cooling, processing and
irrigating water)
Also attaches to boat hulls, docks, locks, breakwaters
and navigation aids, increasing maintenance costs
and impeding waterborne transport.
Characteristics of zebra mussels:
Can attach to hard
surfaces
They have a free-living
planktonic larval stage—
veliger
Females can produce 40,000
veligers
These are typical characteristic of marine species
Veligers are easily transported in bait buckets and
livewells and anywhere else water collects
Adults can attach to hulls and survive outside of
water for several days.
Cover most
hard surfaces
Negative effects
on native clams
Zebra mussels cover
them and prevent them
from feeding and
moving
Plants (> 59 species)
Eurasian Watermilfoil (1881)
Myriophyllum spicatum
Purple Loosestrife (early
1800s)
Lythrum salicaria
How to prevent the spread of aquatic nuisance species?
Never dump bait buckets!!
Before leaving site, inspect gear, boats and
trailers for exotics
Empty all water before leaving site
Rinse your boat and equipment with high pressure
hot water, especially if moored for more than a day
Let equipment dry for several days (does not work
for species with resting eggs)