Exotic Species

I. Impacts of exotics

II. Examples of exotics

III. Origin of exotics

IV. Controlling invasions

Exotic Species

• Exotic = – Introduced– Nonindigenous– Nonnative – Invasive

• >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 Species

a) Predators & Grazers – kill/eat native species

b) Parasites & Pathogens – tiny predators can have lethal consequences on native biota• Chestnut blight, sudden

oak death, avian poxc) Competitorsd) Hybridizatione) Ecosystem effects

Stephens Island wren

Sudden Oak Death

Barred tiger salamander

Change in the abundance of fish eggs and larvae following the arrival of the bloom of the ctenophore (Mnemiopsis) into the Black Sea

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.

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

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

II. Examples of exoticsA. Exotic Animal Species:

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 Moth-considered 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…

http://www.dfg.ca.gov/northernpike/

B. Invasive Plant Species

– early maturation– profuse reproduction by seeds and/or vegetative

structures– 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