3) What makes a species invasive?
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Of species that make it to the wild, only ~10% become
naturalized
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Of species that become naturalized, only ~10% become pests
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
Example:
1000 imported species
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
Example:
1000 imported species
100 escape to wild
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
Example:
1000 imported species
100 escape to wild
10 become naturalized
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
Example:
1000 imported species
100 escape to wild
10 become naturalize
1 becomes pest
3) What makes a species invasive?
An observation:
• “Tens Rule” From Williamson & Fitter (1996) Ecology 77:1661-1666
Only ~10% of imported species escape to wild
Only ~10% of species that make it to the wild become naturalized
Only ~10% of naturalized species become pests
Example:
1000 imported species
100 escape to wild
10 become naturalize
1 becomes pest
If so few species become invasive, does a plant species
become invasive because it has certain characteristics?
3) What makes a species invasive?
Species characteristics:
Nevada’s Coordinated Invasive Weed Strategy: Invasive weeds
often share characteristics such as:
Highly competitive
Cause environmental degradation
Exotic
Easily spread
Highly aggressive
Are difficult to control
Cause economic loss
Augment wildfires
Davis & Thompson (2000): 8 ways to be a colonizer, but only 2 ways
to be an invader
Richardson et al. (2000): Invasive plants are naturalized plants that
produce reproductive offspring (often in large numbers) at
considerable distance from parent plants
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system
• Dioecious (male & female flowers on separate plants) vs.
Monoecious (on same plant)
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system
• Dioecious vs. Monoecious
• Self-incompatible pollen vs. Self-compatible pollen
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1.
•
•
•
Reproductive system
Dioecious vs. Monoecious
Self-incompatible pollen vs. Self-compatible pollen
Some type of asexual reproduction
Apomixis – produce viable seed without fertilization
Vegetative reproduction – regenerate from stem or root fragments
Clonal propogation – new individuals produced through rhizomes
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible monoecious w/
asexual reproduction)
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible monoecious w/
asexual reproduction)
2. Flowering & fruiting periods
• Short vs. Long flowering period
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible monoecious w/
asexual reproduction)
2. Flowering & fruiting periods
• Short vs. Long flowering period
• Short vs. Long fruiting period
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period
• Short vs. long
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production
• Low vs. high
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production (tend to be: high)
5. Germination cues
• Present vs. Absent
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production (tend to be: high)
5. Germination cues (tend to be: present)
6. Light requirements
• Low vs. High ability to capture and efficiently use
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production (tend to be: high)
5. Germination cues (tend to be: present)
6. Light requirements
• Low vs. High ability to capture and efficiently use
• High phenotypic plasticity for light & other resources
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production (tend to be: high)
5. Germination cues (tend to be: present)
6. Light requirements
• Low vs. High ability to capture and efficiently use
• High phenotypic plasticity for light & other resources
• High competitive ability for light & other resources
3) What makes a species invasive?
Species characteristics: Plant Life History Traits (Chapter 3 of NRC
2002)
1. Reproductive system (tend to be: self-compatible & monoecious w/
asexual reproduction)
2. Flowering & fruiting periods (tend to be: long)
3. Juvenile period (tend to be: short)
4. Seed production (tend to be: high)
5. Germination cues (tend to be: present)
6. Light requirements (tend to be: highly efficient, plastic, &
competitive)
3) What makes a species invasive?
SUMMARY: Is it characteristics of the species?
3) What makes a species invasive?
X
SUMMARY: Is it characteristics of the species?
3) What makes a species invasive?
X
SUMMARY: Is it characteristics of the species?
If not simply a characteristic of the species, then is it a characteristic of
the environment?
3) What makes a species invasive?
X
SUMMARY: Is it characteristics of the species?
If not simply a characteristic of the species, then is it a characteristic of
the environment?
Or both species and environment?
3) What makes a species invasive?
X
SUMMARY: Is it characteristics of the species?
If not simply a characteristic of the species, then is it a characteristic of
the environment?
Or both species and environment?
10 hypothesis: (order subject to change)
Vacant niche hypothesis
Environmental change hypothesis
Microevolutionary change hypothesis
Escape from biotic constraints hypothesis
BCW hypothesis
Variable resource availability hypothesis
Competition hypothesis
Biodiversity hypothesis
Disturbance and land use hypothesis
Anthropogenic hypothesis
3) What makes a species invasive?
a) Vacant Niche Hypothesis
“Niche” concept first developed by Grannell in 1917. Found that could
differentiate species of thrushes on the basis of a resource (in his
case, microhabitats)
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Fundamental niche formalized by Hutchinson in 1957.
= theoretical limits of existence for a species along n resource
axes
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Fundamental niche formalized by Hutchinson in 1957.
= theoretical limits of existence for a species along n resource
axes
Realized niche = actual limits of existence for a species
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Success
Fundamental niche – Species A
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Success
Success
Fundamental niche – Species A
Resource axis #1
Resource axis #2
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Fundamental niche – Species A
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Fundamental niche – Species A
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Fundamental niche – Species A, Species B
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Fundamental niche – Species A, Species B
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Fundamental niche – Species A, Species B
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Realized niche – Species A, Species B
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Realized niche – Species A, Species B
Fundamental niche: Invader – Species C
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Realized niche – Species A, Species B
Fundamental niche: Invader – Species C
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
New realized niche – Species A, Species B
Realized niche: Invader – Species C
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Realized niche – Species A, Species B
Realized niche: Invader – Species C
Fundamental niche: Invader – Species D
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
Realized niche – Species A, Species B
Realized niche: Invader – Species C
Fundamental niche: Invader – Species D
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
Resource axis #2
New realized niche – Species A, Species B
Realized niche: Invader – Species C
Realized niche: Invader – Species D
Resource axis #1
3) What makes a species invasive?
a) Vacant Niche Hypothesis
SUMMARY: Vacant niches
• May have some utility for tropical oceanic islands
BUT
• Actual demonstration of “vacant” niche is nearly impossible
• Many potential invaders lack pollinators, symbionts, etc.