Invasive Species

Exposé

Millions being spent on a snake

What a BIG waste of money!

Let’s talk a bit about this snake….Brown tree snake (Boiga irregularis)

• Native to Australia, Papua New Guinea, Solomon Islands

• Brought to Guam (WWII, accidental cargo)

• Has devastated native lizards, birds (8 of 12 ground dwellers now extinct)

Brown tree snake

Guam

Solomon Islands

Guam

Solomon Islands

What about Hawaii?!?!

Other impacts• Power interruptions

• Consumption of poultry, pets

• Attacks on infantsand the disabled...

• Non-native (alien)

• Self-perpetuating

• Expanding populations (or historically expanding)

• Exerts ecological impacts

• Initial introduction due to human activity

Definition of "invasive species"

TimeframeUsually defined post-European settlement

ScaleCan be jump dispersal or range expansion

Non-Native?

Ecological consequences of invasion

• Outcompete native species

• No. 2 cause of species endangerment

• Change community structure

• Alter ecosystem processes

Brown-headedcowbird

Outcompete native species

Asian Bark fungus; Chestnut blight1 in 4 trees were chestnut prior to 1900sAdult trees now virtually extinct

Species endangerment

Europeanbeachgrass

Change community structure

Fire regime (Melaleuca in Everglades)

Change ecosystem processes

Nutrient cycles (Scotch broom in western U.S.)

Hydrologic cycle (salt-cedar in desert southwestern U.S.)

Change ecosystem processes

Human impacts from invasion

• Economic costs

• Health and safety threats

Economic costs

Purple knapweed

Water hyacinth

Waterways

Human structures

Economic costs

Agriculture

Giant Hogweed

Human health impacts

Human health impacts

SMALLPOXSYPHILIS

BIRD FLUHIV

WEST NILESARS

AND MANY MANY MORE!!!

Human health impacts

Does every introduced speciesbecome an invader?

Rule of 10s

10% 10%Imported Introduced Established Invasive

10%

• Disturbance and land-use history

• Cultivation and dispersal dynamics

• Escape of natural enemies, lack of resistance

Environmental factors mediating invasion

Disturbance: Abundance of invasive cinquefoil in different habitats of Oregon

Escape: Catchflyin native vs.introducedrange

• “Pre-adaptation” to environments

• Bottlenecks and genetic diversity

• Rapid adaptation in introduced range

Genetic factors mediating invasion

• Fast growth, rapid maturity

• High dispersal ability

• Generalist ecology

• Single parent reproduction

• Association with humans/disturbance

• Invasive elsewhere

Characteristics of invasives

• Food

• Fiber

• Erosion control

• “Recreational”

• Accidental

Why are non-native species introduced?

Snakehead

Food

Food

Himalayan Blackberry

Fiber

Bamboo

Nutria

Kudzu

Erosion control

Mongoose

Cane toad

Multicolored lady beetle

Pest control

Swan

Purple loosestrife

Recreation: pretty things

PythonFeral cats

Recreation: pets

Accidental

Zebra mussels

Accidental

Cheat Grass

Can invasions be controlled?Lets review the causes of invasion...

• Introduced taxa better competitors

• "Preadaption" to disturbed habitats

• Filling empty ecological niches

• Escaping from enemies

Can invasions be controlled?Lets review the causes of invasion...

• Introduced taxa better competitors

• "Preadaption" to disturbed habitats

• Filling empty ecological niches

• Escaping from enemies

There is a long history of bio-control efforts for invasive species...

Bio-control: introduction of enemies(predators) of pests (native or introduced)

• Rabbits in Australia

• Cacti in Australia

• St. John’s Wort in North America

Bio-control successes

• Mongoose

• Cane toads

• Ladybird beetles

• Grass carp

• African land snail

Bio-control failures

Knapweed Gall Fly Gall Fly Larvae

Deer MouseDeer MouseHanta Virus

Populations have tripled Mice eat 1000+ larvae/night

Fly lays eggs in flowerhead Larvae eat seeds

Increased reservoir of virus

Major invader of rangelands

Unintended consequences of biocontrol

• Reduce new introductions

• Early detection (lag time)

• Isolation

• Manual removal

• Biocontrol

Integrative management of invasive species