Download Exotic Species Invasive Species

Trackers kill mystery tiger roaming
Southern California hills (The Associated
Press,’ February 24, 2005)
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The 425-pound cat
wandered the hills of Simi
Valley near the Ronald Reagan
Presidential Library for more
than a week
Ken Tucker, 45, told KCBS-TV
the tiger walked to a nearby
house and "was just staring
down" the neighbor's dogs.
Invasive Species
Also “exotics” or
“introduced” or
“non-indigenous” or
“alien” species
Exotic Species
“Invasive species are exotic or native
species that displace, destroy, or outcompete native species for food,
space, and water or otherwise
fundamentally alter ecological
processes, thus threatening intact
ecosystems.”
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
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How do they impact native species?
Displacement or replacement?
Homogenization
Can be predators, competitors, parasites, diseases.
“Process in which a mixture is made uniform throughout”.
Can modify habitat.
Biotic homogenization
Can promote spread of other invaders.
Increasing similarity among areas in terms of species identity.
Ultimately…displace native species
Habitat loss and modification coupled with the
widespread introduction of a few species leads
to homogenization.
Black bars = invaded
Open bars = uninvaded
Alpha diversity = number of species locally
Beta diversity = turnover in species from site to site
Gamma diversity = number of species regionally
ants in a variety of habitats in so. California
Birds on islands (from Case 1996 Biol Con)
Characteristics of invasive species
general diet and habitat requirements
high abundance
small body size
high reproductive potential (r-strategy)
good competitors
social / gregarious
Historical versus Current Rates of
Colonization
Hawaiian Islands:
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Galapagos Islands
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Generalities would be nice….
Make invasion biology a more predictive science.
flowering plants colonized at a rate of 1/100,000
before 1778
since 1778 (European arrival) at a rate of 4/year
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1/10,000 unaided
1/2 years since European arrival in 1535
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Since the United States was first
colonized by Europeans, addition
of:
~4,000 exotic plants
~2,300 exotic animals
What are these species?
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Many of these species--such as crop plants and
some game animals--are beneficial
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Others--such as most pets and ornamental
plants--are largely harmless amenities.
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Only about 15 percent are considered "harmful"
(U.S. Office of Technology Assessment 1993).
European Starling
•First successful introduction was 60 European
starlings released in Central Park, NY. in 1890, by
fans of Shakespeare
–competes with
bluebirds,
woodpeckers
House Sparrow
•The House Sparrow was
introduced into Brooklyn,
New York, in 1851.
•Competition from the House Sparrow
for cavity nests can cause decline of
some native species.
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The problem species…
Exotics and Endangered Species
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The harmful 15% have become invaders,
causing widespread problems that can
prove serious and exceedingly costly.
From 1906 to 1991, a scant 79 exotic
species exacted about $97 billion in
economic damages.
Of the 632 species and subspecies recently officially
listed as "endangered" under the Endangered
Species Act
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45 are primarily threatened by competition from
introduced species.
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About 100 species on the list are threatened by introduced
species that prey or feed on them.
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5 are threatened chiefly by exotic diseases carried by
introduced species.
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For 3, a contributing threat is hybridization with introduced
plants or animals.
Domination of ecosystems
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IMPACTS and MECHANISMS
The greatest impacts are caused by plant
species that come to dominate entire
ecosystems.
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Purple loosestrife
Spread of Lythrum
salicaria as of 1900, 1940,
1990
(Lythrum salicaria)
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Also known as the "Purple Plague“
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Hearty European native, graced with stunning
purple flowers
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First taken to New England in the early 1800s
as an ornamental plant.
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Dries wetlands
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Changes habitat structure
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Outcompetes other species
Wet Loamy Soils
TWF005
1Kg
Pump house and water control structure for green-tree
impoundment at Montezuma National Wildlife Refuge in
central New York, 18 June 1968 versus 10 years later
The mixture contains 20% wild flowers
Betony, Black Knapweed, Common Fleabane, Devils
Bit Scabious, Greater Birds-foot Trefoil, Hemp
Abrimony, Marsh Woundwort, Meadow Buttercup,
Meadow Rue, Meadow Sweet, Ox-eye Daisy, Pepper
Saxifrage, Purple Loosestrife, Ragged Robin,
Sneezewort, Square stem St John's Wort, Yellow Flag
Iris and Yellow Rattle
Grasses 80%
Browntop Bentgrass, Chewings Fescue, Common
Sedge, Crested Dogstail, Meadow Barley, Meadow
Foxtail, Pendulas Sedge, Sheep's Fescue, Smooth
Meadowgrass, Sweet Vernal and Tufted Hairgrass.
Tamarisk
(Tamarix spp.)
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Introduced by western settlers in the 1800s
for wood, shade and erosion control
the Eurasian tamarisk tree now infests about
1 million acres.
Otherwise known as “Salt cedar”
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Threats Posed
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Deep roots can suck springs and riparian
zones dry.
“salt cedar” hints at its ability to excrete
salt from leaf glands, making the soil
around it inhospitable to native vegetation.
Feral Hogs
Introduced animal species can change the
entire character of an ecosystem, through its
effects on vegetation and on which plants
will survive.
Effects
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Consume large amounts of food and may
reduce the food supply available for other
animals.
Most serious damage comes from rooting overturn large areas of turf
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Ecological Impacts
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In Great Smokey Mountains National Park hogs
have:
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reduced plant cover by as much as 80%,
increase bare ground by 88%,
reduced the depth of the forest litter by 65%,
reduced the weight of leaf litter by 59%,
exposed 1,400 - 2,800 tree roots/ha,
accelerated decomposition and loss of nutrients from the
forest floor,
altered the nitrogen transformation process in watersheds,
with nitrate-nitrogen in stream water double their usual
levels
A greensword montane bog before
(left) and after feral pig (top photo)
damage (Hawaii)
Chestnut blight (fungus)
Cryphonectria parasitica
Plant pathogens can overwhelm an entire
ecosystem.
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Arrived in New York City in the late 19th century on
nursery stock from Asia
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Only infects the above-ground parts of trees,
causing cankers that enlarge, girdle and kill
branches and trunks.
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Surviving root systems can regenerate to produce
sprouts that grow into small trees.
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These sprouts become infected and die but
sometimes a few nuts are produced first.
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Sprouting and infection cycle continues across the
original range of American chestnut.
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Effects
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In less than fifty years had spread over 225
million acres of the eastern U.S., destroying
virtually every chestnut tree (probably one
billion).
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Chestnut had comprised a quarter or more of
the canopy of tall trees in many forests.
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Staggering ecosystem effects – passenger
pigeons?
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More subtle ones, too: several insect species
that live only on the chestnut are now extinct or
endangered.
Dutch elm disease
Sudden Oak Death
Phytophthora ramorum
Introduced species can also propagate
diseases that harm native species.
Hawaiian islands - introduced Asian songbirds are host to
avian pox and avian malaria.
Transmitted to native birds by introduced mosquitoes
Lead to an almost total elimination of native birds, unique to
Hawaii, in lowland forests.
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The Culex mosquito
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Native birds lack of resistance to avian malaria and
pox carried into their habitat by Culex mosquitoes.
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Culex mosquitoes proliferate during wetter times of
year and bite birds while they sleep.
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Thrive in wet forests up to about 5,000 feet, where
too cool for mosquitoes.
Fire Ant
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And introduced animals can simply attack
native species
The South American fire ant arrived in Mobile,
Alabama around 1940
Since spread throughout the Southeast
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Impacts
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Fire ants are a weed species, that is, a species
that is "adapted for the opportunistic exploitation
of ecologically disturbed habitats"
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Presence of imported fire ants can reduce or
eliminate other insects (esp. ants), spiders,
scorpions, mites, centipedes, and ground-nesting
mammals and birds
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Secondary effects on animals higher on the food
chain such as lizards, snakes, rabbits, and deer
Boiga irregularis
Brown Tree Snake
Another example
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Impacts
Between 1960 and the 1980s, the following birds became extinct on
Guam:
„ Guam Flycatcher
„ Rufus Fantail
„ Brindled White-eye
„ White-throated Ground Dove
„ Cardinal Honey-eater
„ Marianas Fruit-Dove
The following became extinct in the wild, but have been maintained
in captivity:
„ Guam Rail
„ Micronesian Kingfisher
The Culprit
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The spread of the snake since the 1950’s closely
parallels the extinction of the birds -- birds disappear
within a year or so of the snake's arrival.
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The snake is known to feed on birds in its native
range
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Very good at climbing - even onto thin branches.
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Tethered and captive birds are, in 85% of cases,
eaten within one night.
What’s being done?
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As many Rails and Kingfishers as could be
caught were taken into captivity and bred in
captivity.
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Can’t yet re-introduce them to their native habitat
although snake-free zones being established
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Attempts to introduce into similar forest habitat
on Rota, 50 km to the north of Guam
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Of snakes and tylenol…
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80 milligrams of acetaminophen will kill the
brown tree snake.
Delivered inside “pinkies”
So far, does not appear to affect other wildlife
May “relieve Guam of its snake headache”
A last example…
Johnston, J.J., et al. 2002. Risk assessment of an acetaminophen baiting
program for chemical control of brown tree snakes on Guam: Evaluation of
baits, snake residues, and potential primary and secondary hazards.
Environmental Science and Technology 36(Sept. 1):3827-3833.
Suburban predators
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What mammal is responsible for annually
killing 38 million songbirds, four million
cottontail rabbits and 100 million small
mammals just in Wisconsin?
(A) Skunk (B) Fox (C) Raccoon (D) Pine
Marten (E) All of the above (F) None of the
above
Suburban Predators
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In the United States, domestic cats (>60 million in U.S.
homes and perhaps 30 to 40 million more feral) are
estimated to kill:
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over a billion native small mammals
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And, conservatively, 200 million birds annually
Domestic cats have been implicated, to varying degrees,
in:
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the endangerment of at least six species of North
American birds and small mammals,
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the extinction of more than 20 animal species in
Australia.
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End exotics
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