Invasive and Exotic Species

Doyle L. CrosswhiteGeosciences Department

University of Arkansas

What is an invasive species?

U.S Environmental Protection Agency. 2007.

“Invasive species means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.”

U.S. Department of Agriculture. 2007.

“non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”

“Invasive species can be plants, animals, and other organisms (e.g., microbes). Human actions are the primary means of invasive species introductions.”

Charles Elton, 1958

Ecological Explosion- “an enormous increase in numbers of an organism previously held in check by other forces.”

Population Explosion

Natural Barriers to Species Interchange

• Glaciers• Oceans & Currents• Mountain Ranges• Freshwater Bodies• Predation and Competition

How are exotic/alien species become established?

• Ballast Water• Boat Hulls• Aquiculture Escapes• Intentional introductions• Aquaria Releases• Live Food Industry• Vehicular Transport• Escaped Ornamentals

• Cross-basin Connections• Fish Bait Releases• Illegal Stocking• Domestic->Feral• Solid Waste Disposal• Biological Control

Shipping

Some Examples

• Zebra Mussel• Nutria• Ringneck Pheasant• Fire Ant• House Sparrow• European Starling• Bermuda Grass• Mexican Fruit Fly

• Cord Grass, Spartina• Striped Bass• Sea Lamprey• Brown-headed Cowbird• Cattle Egret

Invasive Species in North America

Some Consequences

• Economic• Environmental• Human Health• Agricultural Pests• Species Extinctions

Management of Invasive Species

• Quarantine

• Eradication

• Biological Control

Brown-headed Cowbird, Molothrus ater

Cowbird Biology

• native range- Great Plains

• “brood parasites”

• range expansion

• >220 host spp.

Asiatic Clam, Corbicula

Asiatic Clam• Indigenous to Asia & east to Mediterranean,

Australia and Africa

• North America 1924

• habitat preferences

• high fecundity- 400 larvae/day

• densities- 20,000 clams/m2

Distribution of Corbicula

Questions?