Exotic Species - University of San Francisco

Exotic Species
Impacts of exotics
Examples of exotics
Origin of exotics
Controlling invasions
Exotic Species
• Exotic =
>4,000 plant and 2,300 animal species in the US
Responsible for ~42% of all species listed
Cost us $138 billion annually
Problem with exotics –
I. Impacts of Exotic
a) Predators & Grazers –
kill/eat native species
b) Parasites & Pathogens –
tiny predators can have
lethal consequences on
native biota
Stephens Island wren
Chestnut blight, sudden
oak death, avian pox
c) Competitors
d) Hybridization
e) Ecosystem effects
Sudden Oak Death
Barred tiger salamander
Mnemiopsis is able to live in oxygen poor waters and is not
significantly harmed by water pollution. In addition, this
organism thrives in brackish water that has a high
concentration of organic material suspended in it.
Change in the abundance of fish eggs and larvae following the arrival of
the bloom of the ctenophore (Mnemiopsis) into the Black Sea
Success Rates – why some last,
and others don’t…
 Most imported species perish unless
nurtured by humans
 Increased # of introductions increases
chance of success
• Islands more sensitive
II. Examples of exotics
A. Exotic Animal Species:
1) Argentine Ants - They may eat nestling birds. They out
compete native insects for food and habitat and consume or
displace natural predators such as lizards, snakes, and spiders
2) Fire ants, replaced the two native species
3) Asian Longhorn Beetle
-destroyed hardwood trees in more than
a half-dozen U.S. states a year after it
was first reported (1999)
4) Gypsy Mothconsidered one of the
most important pests
of red and white oaks
in the Northeast
5) Isopod Sphaeroma
quoyanum, introduced in 1893,
burrows into the mud banks
and thus increases the erosion
rate of the salt marsh
6) the green crab has been associated with tenfold decreases in
both native shore crabs (Hemigrapsus oregonensis) and clams
(Nutricola tantilla); preliminary experiments show green crabs
readily consume juvenile Dungeness crabs, thus raising concerns
about impacts on this fishery
7) Zebra Mussel - consume microzooplankton and have been shown to have a
large impact on both the total biomass and relative abundance of zooplankton in
systems other than inland lakes. Out compete natives, gum up waterways…
On Jan. 6, quagga mussels (close relative
of zebra mussel) were discovered in Lake
Mead, which straddles the Nevada-Arizona
border and connects to Southern California
via the Colorado River and a system of
aqueducts and canals.
8) Rana catesbeiana competes with native anurans. Larvae can have a significant
impact upon benthic algae, and thus perturb aquatic community structure. Adults
may be responsible for significant levels of predation on native anurans and other
aquatic herpetofauna, such as snakes and turtles
9) Brown Tree Snake: Has virtually wiped out the native forest birds of Guam,
including the flightless rail. Twelve species of bird unique to the island have
disappeared as a direct result of brown tree snake predation (See Fig. 9.3)
10) Sea Lampreys were a major cause of the collapse of lake trout, white fish and
chub populations in the Great Lakes during the 40’s and the 50’s. Today, lamprey
consume host blood, primarily from lake trout in the Great Lakes.
-one sea lamprey can kill 40 pounds or more of fish
11) Major ecological impact of Starlings is driving out competitors. Because starlings
are so aggressive and gregarious, they force out many native species. Starlings may
attack established nests of other species destroying the eggs. An overabundance of
starlings causes a lack of avian diversity
12) Red Fox - since the early 1980's, it has been gradually
exterminating several endangered species of birds in coastal
wetlands. It eats the eggs of the light-footed clapper rail, which
is an endangered species.
13) Northern Pike – Native of Alaska, has
invaded California…
B. Invasive Plant Species
– early maturation
– profuse reproduction by seeds and/or vegetative
– long life of seeds in the soil
– adaptation for spread
– production of biological toxins that suppress the
growth of other plants
III. What is the origin of exotics?
A. Unintentional “incidents”
B. Intentional “incidents”
A. Unintentional incidents
B. Intentional
1) US office of Plant Introduction,
Acclimatization Societies
2) Subsistence & Commerce
3) Recreation
Kudsu - a vine that when left uncontrolled will eventually grow over almost any
fixed object in its proximity including other vegetation. During the Great Depression
of the 1930s, the Soil Conservation Service promoted kudzu for erosion control.
Hundreds of young men were given work planting kudzu through the Civilian
Conservation Corps.
IV. Controlling invasions
• Species-based control
– Physical control – trapping, digging up,
removing invaders
– Chemical control - pesticides, herbicides,
antibiotics, antimicrobials
– Biological control –
• Invasion prevention

similar documents