Download INVASIVE SPECIES - Department of Zoology, UBC

Announcements:
• Midterm paper due next Monday 25 Oct.
• Tutorial next week: Read the description of the
final project on the course website; think about
possible topics.
• Tree data due by next Tuesday 26 Oct.
• Lectures next week (I’ll be away): Kai Chan on
Monday; Judy Myers (Biocontrol) on Wed. (guest
material will be on the final)
COURSE SCHEDULE
I. Foundations of discipline.
II. Scientific underpinnings.
III. Threats to biodiversity.
IV. Solutions.
V. Perspectives & case studies.
Today (& next
Wed.):
Invasion Biology
Last time
(& next time):
Conservation
Economics
• FINAL EXAM: Monday 20 December, 3:30pm
INVASIVE SPECIES
Some exotics in southwestern B.C.
English ivy
Eastern grey squirrel
Should we attempt to eradicate
these and other exotic species?
• The invasion process
• Ecological and economic impacts
• Pathways of introduction
• Predictors of invasive “success”
• Methods of prevention and control
A.Yes
Japanese knotweed
Atlantic salmon
B. No
Himalayan blackberry
C. Depends on the species
House sparrow
1
Some exotic species in North America
THE INVASION PROCESS
Uptake from native range
Transfer via vector
Cattle
Release in new region
Establishment
Tomato
Perennial rye grass
Population increase
& range expansion
Wheat
Williamson & Fitter (1996) Ecology
What fraction of plant
species introduced to a
new continent
ultimately become
“invasive”?
The “tens rule”:
A. 1/2
1/10 species that arrive
will survive
B. 1/5
1/10 species that survive
will establish
C. 1/10
1/10 species that
establish will become
“invasive”
THE INVASION PROCESS
Uptake from native range
Transfer via vector
Release in new region
D. 1/100
Establishment
The tens rule is not
to be taken literally,
but it captures the
result that only a
small proportion of
introduced species
ever actually
becomes a concern
to people
Population increase
& range expansion
E. 1/1000
Williamson & Fitter (1996) Ecology
2
Ecological and economic effects of invasive species
Dilution and competition:
Even if no (little) regional extinction – effects on abundance and local diversity
e.g., Purple loosestrife in temperate wetlands
Ecological impacts
- “Dilution” of native biodiversity
- Direct impact on native species:
competition, predation, disease
- Ecosystem level change
Introduced predators can cause great damage
(including extinction),
particularly on islands with “naïve” prey
Introduced species can alter ecosystem processes
e.g., Exotic plants in Hawaii
C4 grasses increase fire
frequency, alter ecosystem
properties and vegetation change
Hawaii Volcanoes National Park
Brown tree snakes
Feral cats
Exotic nitrogen fixer (Myrica faya)
colonizes volcanic sites, altering
nutrient cycling and succession
Vitousek et al. (1987) Science
Mack & D’Antonio (2001) Ecological Applications
3
Ecological and economic effects of invasive species
Economic impacts
Zebra mussels in eastern North American waterways
Clogging of water intake pipes (among other things)
- Reduce agricultural/pasture productivity
- Forest damage (insect pests)
- Clog water intakes (zebra mussels)
- Choke waterways (aquatic plants)
- Health costs (introduced diseases)
Estimate: ~50,000 non-native species costs
the U.S. economy >$130 billion per year
Pimentel et al. (2000) BioScience
Damage to forests by exotic insects:
The hemlock woolly adelgid
Agricultural pests:
Exotic insects that damage our food plants
European corn borer
4
Some important pathways of introduction
Intentional introduction
- Early European settlers wanting to feel “at home”
- Horticulture and the pet trade
- Food/forage organisms: fish, pasture grasses etc.
- Biocontrol agents
For species that have been
introduced to a new
continent, the most
consistent predictor of which
ones will become invasive is:
A. Reproductive rate
B. Body size
Unintentional introduction
- Ship ballast water
- Grain shipments
- “Stowaways” (e.g., brown tree snake)
Determinants of establishment:
The most consistent predictor of success is “propagule pressure” –
how many individuals introduced and how often
Birds introduced to New Zealand
C. Number of individuals
introduced
D. Habitat/diet specialization
Determinants of establishment:
It has proven difficult to predict success based on species traits,
but there are exceptions…
Introduced fish in the
Great Lakes
Successfully established
Failure to establish
Success or failure to establish correctly predicted for 43/45 species
Veltman et al. (1996) American Naturalist
Kolar & Lodge (2002) Science
5
Determinants of invasion: the enemy-release hypothesis
Degree of “enemy release” predicts invasiveness
of plant species in the U.S.
Proportion of states that
list species as “noxious”
Proportion of organizations that
list species as “invasive”
Determinants of invasion
What makes a habitat more or less invasible?
- Climatic match to tolerances of invaders
- Empty niches (islands)
- Lack of enemies of invaders
- Resource availability
- Disturbance
- Anthropogenic habitats (human commensals)
- Naïve prey (islands)
How many pathogenic fungi & viruses in
introduced range vs. native range
Mitchell & Power (2003) Nature
Are the issues faced with exotic
species any different than those
faced with native species?
Ecology 101:
If we monkey around
with a food web,
major changes can
happen (abundances
of other species,
fluxes of nutrients,
energy, etc.).
BUT, not
necessarily…
6
Prevention, eradication & control of exotic species
Most exotic species are
innocuous, and many native
species have become pests
(pine beetles, deer, etc.)
Prevention
Uptake from native range
Prevention, eradication & control of exotic species
Transfer via vector
Prevention of introduction:
e.g., exchange ballast
water mid-ocean
Transfer via vector
Release in new region
Control Eradication
Control Eradication
Population increase
& range expansion
Population increase
& range expansion
Uptake from native range
Release in new region
Establishment
Establishment
Prevention, eradication & control of exotic species
Prevention
Prevention
Uptake from native range
Transfer via vector
Release in new region
Control Eradication
Are the issues faced with exotic
species any different than those
faced with native species?
Establishment
Population increase
& range expansion
7
Prevention, eradication & control of exotic species
Transfer via vector
Prevention, eradication & control of exotic species
Uptake from native range
Prevention
Prevention
Uptake from native range
Eradication of mammals on islands:
Feral pigs on Santiago Island, Galapagos
~19,000 animals killed by hunting & poison
over 30 years
Transfer via vector
Release in new region
Control Eradication
Release in new region
Control Eradication
Biological control:
Introducing natural enemies to
control invasive species
Establishment
Population increase
& range expansion
Establishment
Population increase
& range expansion
Would be extremely difficult on a mainland
Cruz et al. (2005) Biological Conservation
8