Transcript Slide

Invasive Species
"We must make no mistake:
We are seeing one of the
Great historical convulsions
in the world's flora and
fauna. We might say, with
Professor Challenger,
standing on Conan Doyle's
'Lost World', with his black
beard jutting out: 'We have
been privileged to be present
at one of the typical decisive
battles of history--the
battles which have
determined the fate of the
world.'"
C. S. Elton, The Ecology of
Invasions by Plants and
Animals, 1958
Invasive problems in the U.S.
Lodge et al.
• kudzu (Pueraria lobata) in the SE U.S.
• cheat grass (Bromus tectorum) in western
U.S. crops and rangelands
• zebra mussel (Dreissena polymorpha) in the
Great Lakes region
• the seaweed caulerpa (Caulerpa taxifolia)
• Asian longhorn beetle (Anoplophora
glabrapennis)
• emerald ash borer beetle (Agrilus planipennis)
• sudden oak death (Phytophthora ramorum)
• Viruses: West Nile, monkeypox, and SARS
Melaleuca
in S Florida
• Transpiration
higher
• Lower water table
• Hotter fire
• Deeper burn in
organic matter,
more severe
effects
Economic & other impacts
to human well-being
• Forestry, agriculture
• Boating, fishing, swimming, water
supply
• Allergies, toxins
• Fire: human life and property
• Cost of control
• Environmental cost of toxic chemical
use
Where did the invasive species
problem come from?
• Why is the earth a loaded gun of
biological invasions waiting to
happen?
Darwin (1859):
In considering the distribution of organic
beings over the face of the globe, the first
great fact which strikes us is that
neither the similarity nor the dissimilarity
of the inhabitants of various regions can be
wholly accounted for by climatal and other
physical conditions…
There is hardly a climate or condition in the
Old World which cannot be paralleled in the
New…[yet] how widely different their
organic productions!
Summary 1: Separate evolution in
separate places
A global potential for invasion
Darwin: Why separate creation for separate
deserts
Is MORE SPP a problem?
The Homogocene’s Biodiversity Equation
When does 1+1 not equal 2?
Native Spp
1
Alien Spp
+
1
Total Comment/example
=
2
Complementarity
Daylilies?
1
+
1
=
1
Competition
Japanese
honeysuckle?
1
+
1
=
<1
Changed process
Melaleuca in Florida
Myrica in Hawaii
Where did the invasive species
problem come from?
Part 2
Darwin (1859):
There is no exception to the rule that every
organic being naturally increases at so high
a rate, that, if not destroyed, the earth
would soon be covered by the progeny of a
single pair.
The elephant is reckoned the slowest
breeder of all known animals...[yet] after a
period of from 740 to 750 years there
would be nearly nineteen million elephants
alive, descended from the first pair.
20,442 worlds of Paulownia
“Walker counted the seed in a Paulownia pod and
found ‘almost exactly 2,000’. He estimated the
number borne on the trees as over 21 million.
If each developed into a plant, which produced
the same number of seeds the next generation,
in the third generation there would be plants
enough to cover 20,442 worlds the size of ours
(American Forestry 25: 1486. 1919).
Coker and Totten, Trees of the
Southeastern States, 1945.
LOSSES: THE ROLE OF NATURAL
ENEMIES
Douglas fir seeds
--after Lawrence & Rediske 1962
100 Seeds dispersed
47 At germination
21 3 month old seedlings
8 One year old individuals
Where did the invasive
species problem come from?
Summary 1 & 2
• Evolution in isolation producing
adapted species which are unable to
reach all appropriate sites
• All species can increase
exponentially
THEREFORE
the potential for invasions
is clear
• BUT NOT ALL SPECIES ARE
INVASIVE
• CAN WE EXPLAIN AND PREDICT
INVASIONS?
• AN OUNCE OF PREVENTION IS
WORTH A POUND OF CURE…
What does science tell us about invasions
and how might we use that information in
prevention?
5 invasion hypotheses
• 1a-d. Innate biology: Weediness,
competitiveness, tolerance,
preadaptation
• 2. Enemy release/Biotic resistance
• 3a-c. Community invasibility:
diversity, productivity, disturbance
• 4. Availability
• 5. Rapid evolution of invasiveness
2. Enemy release hypothesis (ERH)
Biotic resistance hypothesis (BRH)
Mitchell & Power 2003
Resources X Enemy Release
Blumenthal 2005. Science 310:243-244.
Digression: Asia as a source
of invasive plants & diseases
Close taxonomic relationship has its own
problems
Specialized pests & diseases
Chestnut blight, Dogwood anthracnose,
Balsam & Hemlock woolly adelgids
MANY OTHERS!
THE COEVOLUTIONARY HYPOTHESIS
Bounded variation among enemies
Persistence of the plant and its enemies
results from a balance involving
virulence, dispersal, and increase rate of
the enemy
AND
defense, dispersal, and increase rate of
the host
Biological control tries to reestablish this
coevolutionary context
What does science tell us about invasions
and how might we use that information in
prevention?
5 invasion hypotheses
• 1a-d. Innate biology: Weediness,
competitiveness, tolerance,
preadaptation
• 2. Enemy release/Biotic resistance
• 3a-c. Community invasibility:
diversity, productivity, disturbance
• 4. Availability
• 5. Rapid evolution of invasiveness
5 invasion hypotheses:
What to do
1a-d. Innate biology: Weediness, competitiveness, tolerance,
preadaptation: SOME SPP ARE INVASIVE, PROHIBIT THROUGH
RISK ASSESSMENT, DEVELOP STERILE CULTIVARS—YES
2. Enemy release/Biotic resistance: MANY SPP ARE INVASIVE,
ESPECIALLY THOSE WITH HIGH GROWTH RATES AND HIGH
RESOURCE DEMANDS, ASSESS ROLE OF ENEMIES—YES, but
research is demanding
3a-c. Community invasibility: diversity, productivity, disturbance:
SOME COMMUNITIES ARE INVASIBLE, MANAGE AGAINST
INVASION, MANAGE AGAINST DISTURBANCE AND HIGH
RESOURCE LEVELS, MANAGE FOR HIGH NATIVE RICHNESS—
SOMETIMES, but not always feasible (disturbance, low richness,
high resources are natural, too)
4. Availability: MOST SPP ARE INVASIVE, REDUCE
AVAILABILITY—YES
5. Rapid evolution: RESTRICT GENETIC DIVERSITY—YES, but
seems unlikely given horticultural interest in selection