Introduction To Invasive Plant Ecology

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Introduction To Invasive Plant Ecology

• Bruce Maxwell
• LRES 580 Invasive Plant Ecology

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Thematic Concepts

• Importance of precise terminology in science
• Scientific assessment of media defined issues
• The scientific approach in biology
• Complexity in biology results in lack of
  understanding, but management decisions must be
  made

3
Outline

• History of Invasion Biology
• Invasion Biology Terminology
• Important Ecological Concepts covered in this
  class
• Traits of plant invaders
• Plant community invasibility
• Management in the context of the whole

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History of Invasion Biology

• Charles Elton.1958. The Ecology of Invasions by
  Animals and Plants.
• R.H. MacArthur E.O.Wilson. 1963, 1967. Island
  Biogeography
• J. Harper. 1977. Population Biology of Plants
• Biological Invasions. 1999-present. Journal
• Weed Ecology (primarily in agroecosystems)
• Radosevich Holt, 1984. Weed Ecology
• Cousens Mortimer. 1995. Dynamics of Weed
  Populations

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Applied Plant Invasion Biology

• Biotic Invasions

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Biotic Invasions
Place of Origin
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Biotic Invasions
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Planet of the Weeds -D. Quammen

• Are we causing the sixth extinction?
• Nature Abhors a Vacuum or Invasive spp displace
  natives?
• What are the natural background rates of
  speciation/introduction and extinction?
• The River Tweed vs Hawaii

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Immigrant Weed Species Can Fail... And most do
fail

• River Tweed (Wool Manufacturing), U.K.

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Immigrant Weed Species Can Fail... And most do
fail

• River Tweed (Wool Manufacturing), U.K.
• 1919 348 alien weed species (most burs)
• 52 from other continents
• - Hayward and Druce, 1919
• 1961 Four species spread beyond woolen mill
  grounds - Salisbury, 1961
• 1987 None of the species were found in the
  region - Crawley, 1987

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Marcus, A.W., G. Milner and B. Maxwell. 1998.
Spotted knapweed distribution in stock camps and
trails of the Selway-Bitterroot Wilderness. Great
Basin Nat. 58156-166.
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Forest Canopy
Open Closed
6 0
10 14
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Weeds On The Serengeti Plain of Tanzania
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Terminology
Eight ways to be a colonizer Two ways to be an
invader
Davis and Thompson, 2000
Dispersal Distance
Short
Long
Uniqueness to the region
Common Novel
Common Novel
Impact on the environment
Small Great
Small Great
Small Great
Small Great
Colonizer type
1 2 3 4 5 6
7 8
Novel, invasive colonizers
Successional colonizers
Novel, noninvasive colonizers
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Processes Allowing Naturalization and Transition
to Invasive

• Hypotheses that allow naturalization and
  invasion
• Enemy Release
• Highly competitive
• Extra resources
• New niche with little overlap
• Competitive release from generalist predators or
  herbivores
• Disturbance for colonization

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Transformation from immigrant to invader
the lag phase
Opuntia aurantiaca in South Africa
Moran and Zimmerman, 1991
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Transformation from immigrant to invader

• The number, arrangement of infestations and
  frequency of arrival of immigrants.
• Limits on detection of population growth
• Natural selection improving fitness
• Habitat frequency (including alteration)
• The vagaries of environmental hazards (frequency
  and intensity).

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Identifying Future Invaders

• Taxonomic relationships
• Biological traits

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Diagram Illustrating the Relationship of all
Variables Used in Determining Weeds Of National
Significance In Australia
Weeds of National Significance
Invasiveness Criterion
Impacts Criterion
Potential for Spread Criterion
Socioeconomic and Environmental Criterion
Current Distribution
Future Distribution
Social Index
Economic data for Agric. Forestry (current cost
of control)
Environmental Index
Communities Impacted
IBRA Regions Affected
Monoculture Potential
Species Threatened
The Determination of Weeds of National
SignificanceBy John R Thorp Rod LynchISBN 0
642 44913 9
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Reichards Classification SystemReichard, S.H.
and C.W. Hamilton, 1997. Predicting invasion of
woody plants introduced into North America.
Conservation Biol. 11193-203.

• Used a discriminate analysis model to predict
  woody plant invaders 86.2 accurate
• Decision tree results

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Plant Community Vulnerability To Invasion

• Generalized Hypotheses
• Vacant niche
• Community species richness (Elton,1958 vs
  Londsdale, 1999)
• Escape from biotic constraints
• Disturbance before or upon immigration (invaders
  require disturbance or natives cant tolerate
  disturbance)

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Vacant Niche Hypothesis
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Vacant Niche Hypothesis
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Plant Community Vulnerability To Invasion

• Generalized Hypotheses
• Vacant niche
• Escape from biotic constraints
• Community species richness (Elton,1958 vs
  Londsdale, 1999)
• Disturbance before or upon immigration (invaders
  require disturbance or natives cant tolerate
  disturbance)

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Escape from biotic constraint hypothesis
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Plant Community Vulnerability To Invasion

• Generalized Hypotheses
• Vacant niche
• Escape from biotic constraints
• Community species richness (Elton,1958 vs
  Londsdale, 1999)
• Disturbance before or upon immigration (invaders
  require disturbance or natives cant tolerate
  disturbance)

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Community Species Richness Hypothesis
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Plant Community Vulnerability To Invasion

• Generalized Hypotheses
• Vacant niche
• Escape from biotic constraints
• Community species richness (Elton,1958 vs
  Londsdale, 1999)
• Disturbance before or upon immigration (invaders
  require disturbance or natives cant tolerate
  disturbance) (Huston, 1994)

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Disturbance Hypothesis
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Plant Invasion Dependent On

• Available species pool (propagule pressure)
• Predicting new invasions (ornamentals)
• Thresholds of propagules
• Dispersal potential (properties of exotic spp)
• Available habitat (ecosystem properties)
• Abiotic determinants
• Biotic determinants
• Habitat changes over time (nutrient cycling)
• Relative fitness within habitat (exotic native
  spp prop.)
• Adaptive potential of each species (prop. of
  exotic spp)
• Genotypic variability and phenotypic plasticity

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The Crop Field as a Microcosm To Study Invasion
Spp 4
Spp 1
Spp 5
Spp 2
Spp 6
Spp 2
Spp 3
Spp 7
Available Species Pool
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The Crop Field as a Microcosm To Study Invasion
Spp 4
Spp 1
Spp 5
Spp 2
Spp 6
Spp 2
Spp 3
Spp 7
Dispersal Potential of Each Species
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Potential Habitat
Gradient
Emergence Seedling Survival Produce Viable
Offspring Significant Impact On Crop
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The Crop Field as a Microcosm To Study Invasion
Spp 4
No Crop
Spp 1
Spp 5
Spp 2
Spp 6
Spp 2
Spp 3
Spp 7
Habitat Available for Each Species