Invasive species

Species extinction rates

Causes of Endangerment forImperiled Species in the U.S.

0

10

20

30

40

50

60

70

80

90

100

Habitat destruction

Non-native spp.

Pollution

Overharvest

Disease

Wilcove et al. 1998 (data from U.S. Federal Register)

What are invasive species?

Natives vs. non-natives Introduced Aliens Exotics Adventives/casuals Naturalized

What are invasive species?

Federal Government’s Executive Order defined as:

an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health

Acceleration of introductions

Rates of species introductions in Hawai’i Natural rate: 1 established introduction every

100,000 years After Polynesians: 1 established introduction

every 50,000 years Since Europeans: 1 established introduction

every 0.25 years, or 4 per year Approximately 1000 plant species

established in the last 200 years out of about 5000 introduced

History of the study of biological invasions

Darwin’s Origin of the Species (1859) C. Elton’s book in 1958 Early 1980’s, biological invasions began to be

recognized as problematic: call for assessment of scientific understanding

In the early 90’s, invasions were still not given too much attention

1999 – BIG CHANGE An executive order required all federal agencies to refrain

from activities that contribute to introduction and spread of invasives

How do introductions happen?

Most introduced species do not survive Of those that survive, many do not cause

“severe harm” to native ecosystems, species or humans (only 15% of establishments)

How do introductions happen?

IntentionalThere is a perceived human benefit from introduction

For example: Food

Pigs, goats, birds, sheep, crops “Friends”

Accidental Hitchhikers

Insects and weedsRats, mice

How do introductions happen?

Natural range expansion Ex: Barred Owls have

moved westward into Spotted Owl range Prey Habitat Hybridization

Invasiveness

Undisturbed systems are not safe from invasion

How do you know if a species will

become invasive? Has it invaded elsewhere? Is the introduction within a range

with similar environmental conditions? Vector? Continued vector?

Vectors

Vector Vehicle or carrier that is able to transfer species,

or route of transmission Examples of vectors of invasive species

Ships Visitors

Other organisms

Characteristics of good invaders

Tolerant of wide range of environmental conditions Originate from area with diverse biota Generalist diet Ecological range overlaps with potential vectors Natural population controls not present

For example: predators, disease, competition

Abundant within large native range r selected life history traits

Life History Traits

 r (fast species)

Unstable environment, density independent

K (slow species)

Stable environment, density dependent interactions

Organism size Small Large

Energy used to make each individual Low High

# Offspring produced Many Few

Timing of maturation EarlyLate

(with much parental care)

Life expectancy Short Long

Lifetime reproductive events One More than one

Impacts of invasives

Cost Ecological

Ecosystem properties and processes Disturbance regimes

Hydrology Native species loss

Predation Hybridize- homogenization of unique regional biota Competition Disease

Disturbance Regime

Cheat Grass (Bromus tectorum)

Hydrology

American Beaver (Castor canadensis)

Anderson et al. 2006

Impacts of invasives

Cost Ecological

Ecosystem properties and processes Disturbance regimes

Hydrology Native species loss

Predation Hybridize- homogenization of unique regional biota Competition Disease

Predation

Brown tree snake (Boiga irregularis)

Introduced predators can alter community structure including trophic structure

From Groom et al (2006)

Predation

New Zealand Grey (A. superciliosa superciliosa)

Hawaiian (A. wyvilliana)

Florida Mottled (A. fulvigula fulvigula)

Rhymer & Simberloff, 1996

Mallard ducks (Anas platyrhynchos)

theyangpa.tripod.com/

Hybridization

Competition

Disease

Asian songbirds host to avian pox and avian malaria

What do we do about invasives?

Education, community support Prevention

Quarantine, monitoring/early detection, emergency response Eradication

Must be done early Need community support

Control Ongoing, costly Containment, priority-site, biological control

Biodiversity conservation Biotic resistance hypothesis (Elton 1958)

Some of the worst invaders

MAMMAL brushtail possum (Trichosurus vulpecula) domestic cat (Felis catus)

goat (Capra hircus) grey squirrel (Sciurus carolinensis)

macaque monkey (Macaca fascicularis) mouse (Mus musculus)

nutria (Myocastor coypus) pig (Sus scrofa)

rabbit (Oryctolagus cuniculus) red deer (Cervus elaphus)

red fox (Vulpes vulpes) ship rat (Rattus rattus)

small Indian mongoose (Herpestes javanicus) stoat (Mustela erminea)

REPTILE brown tree snake (Boiga irregularis) red-eared slider (Trachemys

scripta)

BIRD Indian myna bird (Acridotheres tristis) red-vented bulbul (Pycnonotus cafer)

starling (Sturnus vulgaris)

AMPHIBIAN bullfrog (Rana catesbeiana) cane toad (Bufo marinus)

Caribbean tree frog (Eleutherodactylus coqui)

**From www.issg.org – 100 of the world’s worst invasive alien species

The palila (Loxioides bailleui)

Endangered Restricted population

The palila (Loxioides bailleui)

Food: mamane pods

and flowers, native caterpillars in pods

Introduced parasitic wasps (94% parasitism at lower elevational range of palila)

The palila (Loxioides bailleui)

Rats, mice, mongoose, feral cats, goats Alien grasses, increased fire risk