Download 07 ICA7 Invasion Rubric

LECTURE 17 INVASION ECOLOGY
1) What’s the difference between an introduced Non-native or exotic species moved
accidentally or deliberately to new ecosystem vs. invasive introduced species
that spread after establishment species?
2) What are examples of introduced species in Illinois? Emerald ash borer, long-horn
beetle, purple loosestrife, zebra mussel, garlic mustard…..
3) What are the three stages required for an introduced species to become invasive?
A. arrival
B. establishment
C. spread
ARRIVAL
4) What are general mechanisms by which species are deliberately introduced?
immigrants bringing from native country; Shakespeare fans; game animals; domestic animal
What is one specific example of a specific species that was introduced deliberately?
starling Why was it introduced? occurs in Shakespeare; fan wanted all here.
5) What are general mechanisms by which species are accidentally introduced?
ship ballasts; unprocessed wood; fruit shipments; by-pass natural barriers
What is one specific example of how your own actions might cause an introduction?
on shoes or in luggage when return from foreign country; throw out of our cars
ESTABLISHMENT
6) What are traits of introduced species that make them more likely to be successfully
established?
1. non-specific diet and habitat needs 2. self-fertilization
3. small body size
4. high reproductive potential (r-strategy)
5. good competitor
6. social/ gregarious
SPREAD
7) What are three hypotheses that explain why an introduced species successfully spreads?
A. escape from natural enemies
B. increased competitive ability
C. pre-adapted to disturbed habitats
8) What are three general mechanisms by which introduced species displace (eliminate) native
species?
A. Can act as predator, competitor, parasite, pathogen
B. Can modify habitat
C. Can promote spread of other invaders
9) Relative to other causes, how important are invasive species as threats to endangered species?
They rank #2 – behind habitat degradation and loss; ahead of pollution, overexploitation,
disease.
10) Explain this argument: It does not matters whether a species is displaced because the lost
species is replaced by the new species in a community. The number of species stays the
same. One species plays the same as another in the community so the identity does not
matter. An introduced species will play no havoc.
Do you agree with the argument that replacement of a native species by an introduced
species is no problem? Why or why not? No. The introduced species may have
similar traits, but it may not have its native enemies to control it. It may be more
competitive than the native species and replace more than 1 species.
11) Human activities are resulting in “biotic homogenization”. Explain this statement.
As we destroy and modify habitats, we have fewer diverse habitats. Also as we introduce
species that become widespread and display local native species, widespread areas
become more similar in terms of types of habitats and species within them. Diverstiy
is lost.
12) What are four hypotheses that relate to the types of ecosystems that are particularly
vulnerable to invasion by introduced species?
A. Biotic resistance to invasion via high species diversity.
B. Disturbance with fewer species and more open niches allows invasion.
C. Human areas have many species that have been associated with humans for a long time.
D. Species on islands have little evolutionary history with competitors and natural enemies.
13) Summarize what are the major ecological (not economic) costs of invasive species.
They displace native species; alter native species’ interactions; modify habitat; change
ecosystem processes
14) What are three ways in which we attempt to control invasive species?
A. use of pesticides and herbicides
B. biological control via introduction of a natural enemy from native range.
C. minimize disturbance to landscape
What are problems associated with use of pesticides/herbicides?
Can kill more species than the targeted invasive species.
Can be a selective agent for resistance to the pesticide.
Can pose health risks to humans
What are potential problems with use of biological control?
If it is not species-specific affecting only the invasive species, it can affect other species.
15) How can we prevent problems arising from introduced/invasive species?
Education, research for generalities; monitor for early detection; use quarantine once
found so doesn’t spread; increase regulations
Problem Solving about Invasions….
1. Introduction of Nile perch coincided with a sharp decline in native chiclid fish populations.
Develop a hypothesis to explain the sharp decline in native fist.
If the introduction of Nile perch caused the decline of cichlid populations. (but what is
a testable prediction?)
How could you test your hypothesis? Possibly compare to other lakes with cichlids but no
perch. Hard to test in one lake because there are many uncontrolled factors besides
perch introduction.
What are 2 alternative hypotheses that explain the decline?
1. A newly introduced cichlid parasite caused the decline.
2. A marked decline in aquatic vegetation on which cichlids feed caused the decline.
3. Big changes in water chemistry causedby agricultural runoff caused the decline.
What is the ‘take-home’ message about causation and proof? Coincidence of two events
does not provide evidence of causation. A control lake is needed for comparison, but finding
two lakes with all other variables except perch present (absent) will be hard to find.
Science doesn’t not generate ‘proof’ of causation; alternative, untested explanations may
explain the observation.
2. What is the ‘natural enemies-escape hypothesis’? An introduced plant that has escaped from
its home natural enemy may explode in population size.
What is biological control? Introduction of the home (usually) natural enemy to control the
introduced plant.
Create a 2 X 2 table showing all 4 possible combinations of
native and introduced plants and herbivores. Put BC in the
appropriate box for the typical ‘biological control’. Put the
pampus grass and rabbits example in the appropriate box.
Introduced
Native Plant
Plant
Introduced BC increase decrease
Herbivore
Native
Grass-rabbit increase
Herbivore decrease
What is a meta-analysis such as Parker et al. completed? An analysis of many studies testing
whether a hypothesis is supported, on average, across all studies; to see if there is any
generality (consensus) among all the studies.
What is its end product? An average strength of effects among the studies.
Transfer the data from Parker’s figure to your box, using arrows to show increased/decreased
plant abundance.
Does the meta-analysis support the use of introducing the natural enemy to control an
introduced plant? No; an introduced herbivore’s effect on plant abundance is lower than
the effect of a native herbivore.
Explain the results for a) the introduced herbivore…
The introduced plant has an evolutionary history with its home herbivore and has evolved
some defenses to protect it from this herbivore
b) the native herbivore…The introduced plant faces many native generalist herbivores and
has no evolved defense against them.
What is the problem with the usual experimental design of testing an introduced herbivore
against its former, now introduced plant? The distinction between the effects of native and
introduced herbivores could not have been discerned in a single study, such as the rabbitgrass study, unless both native and introduced herbivores had been used in the same study.
3. Klironomos inoculated 4 old field plant species with 4 species of mycorrhizae; the fungi
were from home (Ontario) and foreign (Quebec) What is the main result?
The response of the plants to the fungi depended on the particular combination of plant
species and fungal species; results were not consistent between ‘home-home’ and ‘homeforeign’ combinations of the same two species. Combinations from the same area showed
the strongest effects, both + and -.
What is the result for A. novae-angliae? The direction (mutualistic vs. parasitistic) of the
effect depended on wehterht he two species cam e from the same or different areas.
What is the ‘take-home’ message? Introduced species may escape some of the strongest
inhibiting effects of soil organisms, but may also fail to benefit from other soil organisms
that would have helped them in their native ranges.
4. Black cherry trees in Indiana inhibit seedling recruitment near the parent; seedlings
rarely survive near the parent tree. Hint: It involves one of the +/- interactions…look at
results below…
Generate a hypothesis/prediction to explain this observation.
If….Soil-borne pathogens control seediling recruitment near the parent tree,
then…seedlings will grow in sterilized soil taken near the parent, but not in non-sterilized
soil taken near the parents.
The results were that seedlings can grow in sterilized soil taken near the parent,
while they don’t grow in non-sterilized soil taken near the parent.
Is there support for your hypothesis? Yes. Explain. The results were as predicted, so there is
support for the hypothesis.
In Europe, seedlings from seeds of Indiana trees grow readily close to the parent.
How would you explain these results? Soil pathogens may be different in Europe and the
seedlings escape from pathogen-caused deaths.