MANAGEMENT OF INVASIVE PLANTS IN THE WESTERN USA
  • Defining the Problem
    • What is a Weed? >
      • Federal Definitions of Noxious Weeds
    • Costs of invasive plants
    • Human Factor
    • Challenges of Invasive Plants
    • Wildfires in the Western USA >
      • Forest Fires: Structure
      • Bark Beetles & Forest Ecosystems
      • Rangeland Fires
    • Climate Change Impacts on Plants >
      • Climate Change: CO2, NO, UV, Ozone Impacts on Plants
      • Climate Change Impacts on Crops
      • Climate Change Impacts on C4 Plants
      • Climate Change Impacts on Rangeland
    • What are we doing?
  • Focus of this Project
    • Why Western States? >
      • Audience for these reports
    • History: Are we doomed to repeat it? >
      • Dust Bowl Re-visited >
        • China: Past & Present
        • UN Biodiversity Report
    • Policy vs. Practice
    • Ecosystems & Economics >
      • Reductionist Approach to science
      • Ecology & Feminism
      • Systems View of Life
      • Ecosystems Health
      • Economic Growth
      • Impact of the Petrochemical Industry
      • Interrelation of Economics & Ecology
    • Federal Agencies >
      • Federal Agencies and Invasive Species
      • History of Coordination with States
      • Challenges of Coordination between Federal Agencies
      • Collaboration or Confusion
    • Organizations to assist landowners
    • Federal Legislation on Invasive Species >
      • 1930s Federal Laws on Invasive Species
      • Federal Seed Act 1939
      • 1940s-1960s Federal Laws on Invasive Species
      • 1970s Federal Laws on Invasive Species
      • 1980s Federal Laws on Invasive Species
      • 1990s Federal Laws on Invasive Species
      • 2000-2010 Federal Laws on Invasive Species
      • 2011-2022 Federal Laws on Invasive Species
      • Federal Bills on Invasive Species not passed
      • Executive Orders on Invasive Species
      • Federal Excise Taxes
    • State Laws and Lists of Noxious Weeds
    • My Inspirations
  • Why we need plants
    • Native Plants
    • Plant Resources
  • Invasive Success Hypotheses
    • Unified Framework
    • Role of Diversity >
      • How Ecosystems Maintain Diversity
      • Fluctuation Dependent Mechanisms
      • Competition-based coexistence mechanisms
      • Niche Differences
      • Species Richness
    • Enemy Release Hypothesis
    • Constitutive Defense Mechanisms
    • Evolution of Increased Competitive Ability
    • Role of Microbes
    • Indirect Defense Mechanisms
    • Novel weapons hypothesis
    • Evolutionary Shifts
    • Resource Allocation
    • Evolutionary Dynamics >
      • Pre-introduction evolutionary history
      • Sampling Effect
      • Founder Effect
      • Admixture, hybridization and polyploidization
      • Rapid Evolution
      • Epigenetics
      • Second Genomes
    • Role of Hybridization
    • Role of Native Plant Neighbors
    • Species Performance
    • Role of Herbivory
    • Evolutionary Reduced Competitive Ability
    • Summary Thoughts on Research
  • Historical Record
    • Regional Conferences
    • Timeline
  • Innovative Solutions
    • Agricultural Best Practices >
      • Ecologically based Successional Management
      • Perennial Crops, Intercropping, beneficial insects
      • Soil Solarization
      • Natural Farming
      • Permaculture
      • Organic Farming
      • Embedding Natural Habitats
      • Conservation Tillage
      • Crop Rotation
      • Water Use Practices
      • Tree Planting: Pros & Cons
    • Grazing Solutions >
      • Sheep and Goat Grazing
      • Cattle & Sheep Grazing
      • Cattle and Bison Grazing
      • Grazing and Revegetation
    • Rangeland Restoration >
      • Federal Goals for Rangelands
      • Novel Ecosystems
      • Prairie Restoration >
        • Prairie Restoration Workshop
        • Weed Prevention Areas
        • California grassland restoration
        • Selah: Bamberger Ranch Preserve
      • Sagebrush Steppe Restoration >
        • Low Nitrogen in Sagebrush Steppe
      • Revegetation with Native Plants
      • Dogs as detectors of noxious weeds
    • Nudges
  • Biological Control
    • Insects as Biocontrol >
      • Impacts of Biocontrol Agents on Non-Target Species
      • Indirect Impact of Biocontrol on Native Species
    • Challenges of Using Biocontrols >
      • DNA studies on Biocontrol Insects
      • Biocontrol takes time
    • Prioritization process for Biocontrol Programs
    • Evolutionary changes impact Biocontrol
    • Vertebrates as Biocontrol Agents
  • Herbicides: History and Impacts
    • Effectiveness of Herbicides in Agricultural Lands
    • Effectiveness of Herbicides in Rangelands
    • History of Use of Herbicides and Pesticides Prior to and During WWII
    • Herbicide use during and post-World War II >
      • 2,4-D Herbicide Use
      • 2,4-D and 2,4,5-T, post-World War II
    • Modern use of Herbicides >
      • Atrazine Herbicide
      • Dicamba Herbicide
      • Glyphosate Herbicide
      • Paraquat Dichloride
      • Picolinic acid family of herbicides >
        • Picloram (Tordon 22K) Herbicide
        • Triclopyr Herbicide
    • Herbicide Resistance in Invasive Plants >
      • Herbicide Resistant Crops
      • Controlling herbicide-resistant weeds in herbicide-resistant crops
      • Best Management Practices
    • Myth of the Silver Bullet
    • Myth of Eradication
    • Merging of Agrochemical Companies
    • Impacts of Pesticides on Environment and Human Health >
      • Pesticide Drift
      • Impacts of Pesticides on Biological Diversity
      • Impacts of Herbicides on Native Plants
      • Pesticide Impacts on Insects >
        • Butterflies: The Impacts of Herbicides
        • Monarch Butterflies: Impacts of Herbicides
      • Impacts of Pesticides on Wildlife >
        • Reptiles & Amphibians: Pesticide Impacts
      • Pesticide Residue in Foods
    • Funding for Research on Pesticides
    • Commentary on Herbicide Use
  • Interviews
    • Interviews Biocontrol >
      • Biocontrol Wyoming
      • Montana Biocontrol Interview Maggio
      • Montana Biocontrol Interview Breitenfeldt
    • California Interviews >
      • Robert Price
      • Doug Johnson
    • Colorado Interviews >
      • George Beck Interview
      • Scott Nissen Interview
    • Idaho Interviews >
      • Purple Sage Organic Farms in Idaho
    • Montana Interviews >
      • Jasmine Reimer Interview Montana
      • Organic Farms Montana Interviews
    • Texas Interviews
    • Washington Interviews >
      • Ray Willard
    • Wyoming Interviews >
      • Slade Franklin Interview
      • John Samson Interview
    • Wyoming Weed and Pest Districts >
      • Josh Shorb Interview
      • Slade Franklin Interview 2
      • Lars Baker Interview
      • Steve Brill Interview
      • George Hittle Interview
      • Peter Illoway Interview
      • Robert Jenn Interview
      • Sharon Johnson Interview
      • Larry Justesen Interview
      • Gale Lamb Interview
      • Stephen McNamee Interview
      • Allen Mooney Interview
      • Rob Orchard Interview
      • Robert Parsons Interview
      • Dick Sackett Interview
      • Comments by Delena
    • NRCS Interviews: Wyoming
  • Western Weed Control Conference 1940s Minutes
    • 1942 Conference
    • 1945 Conference
    • 1946 Conference
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    • Texas Road Logs
    • Wyoming Road Logs
  • Bibliography

Role of Hybridization in Biological Invasions

Photo: Wild Mustard, southwest Montana. © 2020 Delena Norris-Tull
​
The Role of Hybridization in Biological Invasions

Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, July 2020.
 
Ellstrand and Schierenbeck (2000) point out that it is very challenging to determine what causes invasive success for several reasons: very few species become invasive in new environments; many species that become successful invaders only do so after an extended period of time in the new environment; and many only become invasive after being introduced to the new environment multiple times. They propose an evolutionary model to help explain invasive success. “Hybridization between species or between disparate source populations may serve as a stimulus for the evolution of invasiveness.” They reviewed a number of cases in which, “hybridization preceded the emergence of successful invasive populations.” Species with a history of hybridization may have some genetic benefits. A number of the cases they reviewed had significant time lag (many tree and shrub species had been in the new environment more than 100 years, and it is likely that many herbaceous species had been introduced over decades) and had experienced multiple introductions. These conditions may be necessary in order for previously isolated introduced species to come into contact with other populations, and for hybridization to occur.
 
Ellstrand and Schierenbeck, 2000, do not believe that this model fits all invasive species, but that it may be a useful mechanism to consider in future research. They point out that many hybridization events do not result in invasiveness. They propose that for many species, invasiveness may not be inherent when the species arrive in the new environment, but that evolutionary pressure can result in hybridization that may facilitate invasiveness.
 
Ellstrand and Schierenbeck, 2000, point out that the fact that some species are readily controlled by biological agents brought over from their home environment, is an indicator that evolution occurring after introduction is not a factor for those species. But the fact that various invasive species do not respond well to biocontrol, presents the possibility that evolutionary changes occurring within the species within the new environment are an important factor, particularly among plant species. Many native and non-native plant populations that have previously been isolated have been shown to rapidly hybridize when they are no longer isolated. And, due to the ability of numerous plant species to undergo polyploidy (in which the chromosomes of both parents are combined), plants more readily hybridize across species lines, than do animal species, although some animal and pathogen hybrids have also resulted in invasive species. Polyploidy in plant species that have hybridized with related species have created offspring so genetically divergent from either parent species, that the offspring represent a genetically new species.
 
To examine support for their hypothesis, Ellstrand and Schierenbeck, 2000, examined a large number of cases of plant hybridization, and they found that plant hybrids are more common among perennial herbaceous plants than among annuals or woody species, and their paper provided some of the related research that helps explain this tendency. They presented 25 cases of well documented plant hybridization, including both invasive and non-invasive species, to exemplify their hypothesis. Some were hybrids of divergent populations of the same species, and some were related species. The hybrids that have become successful invasive species tended to have one or more of the following genetic advantages in the invaded environment: the development of woodiness, making the hybrid more challenging to remove from an agricultural environment; greater tolerance to climatic ranges, such as temperature tolerance; the ability to out-compete the parent populations; a novel set of traits not present in the parent populations, that enables the hybrid to move into new niches not occupied by the parents; increased genetic diversity; fixed heterosis (new traits that perform better than in either parent population).
 
Ellstrand and Schierenbeck, 2000, point out that the following anthropogenic (human-induced) activities “could enhance both the likelihood of hybridization and the likelihood of creating new niches that favor hybrid derivatives.”
  • Bringing together previously isolated populations. Modern, rapid and long-distance transportation, and large-scale agricultural activities accelerate these events.
  • Opening new niches, due to ecological disturbance.
 
Unfortunately, as with much of the research on invasive species, not enough funding has been available to thoroughly assess their hypothesis.

Reference:
  • Ellstrand, N.C., & Schierenbeck, K.A. (Jan. 27-29, 2000). Hybridization as a stimulus for the evolution of invasiveness in plants? Paper presented at the National Academy of Sciences, Irvine, CA. Reprinted in Euphytica (2006), 148, 35-46.

Next Sections on research on the success of invasive species:
Native Plant Neighbors
species performance
the role of herbivory
evolutionary reduced competitive ability
summary thoughts on the research
Copyright: Dr. Delena Norris-Tull, July 2020. Management of Invasive Plants in the Western USA.

These webpages are always under construction. I welcome corrections and additions to any page.
​Send me an email, and I can send you the original Word format version of any page you wish to correct.
contact Dr. Norris-Tull
Bibliography
who am i?
My work
my inspirations
my adventures
  • Defining the Problem
    • What is a Weed? >
      • Federal Definitions of Noxious Weeds
    • Costs of invasive plants
    • Human Factor
    • Challenges of Invasive Plants
    • Wildfires in the Western USA >
      • Forest Fires: Structure
      • Bark Beetles & Forest Ecosystems
      • Rangeland Fires
    • Climate Change Impacts on Plants >
      • Climate Change: CO2, NO, UV, Ozone Impacts on Plants
      • Climate Change Impacts on Crops
      • Climate Change Impacts on C4 Plants
      • Climate Change Impacts on Rangeland
    • What are we doing?
  • Focus of this Project
    • Why Western States? >
      • Audience for these reports
    • History: Are we doomed to repeat it? >
      • Dust Bowl Re-visited >
        • China: Past & Present
        • UN Biodiversity Report
    • Policy vs. Practice
    • Ecosystems & Economics >
      • Reductionist Approach to science
      • Ecology & Feminism
      • Systems View of Life
      • Ecosystems Health
      • Economic Growth
      • Impact of the Petrochemical Industry
      • Interrelation of Economics & Ecology
    • Federal Agencies >
      • Federal Agencies and Invasive Species
      • History of Coordination with States
      • Challenges of Coordination between Federal Agencies
      • Collaboration or Confusion
    • Organizations to assist landowners
    • Federal Legislation on Invasive Species >
      • 1930s Federal Laws on Invasive Species
      • Federal Seed Act 1939
      • 1940s-1960s Federal Laws on Invasive Species
      • 1970s Federal Laws on Invasive Species
      • 1980s Federal Laws on Invasive Species
      • 1990s Federal Laws on Invasive Species
      • 2000-2010 Federal Laws on Invasive Species
      • 2011-2022 Federal Laws on Invasive Species
      • Federal Bills on Invasive Species not passed
      • Executive Orders on Invasive Species
      • Federal Excise Taxes
    • State Laws and Lists of Noxious Weeds
    • My Inspirations
  • Why we need plants
    • Native Plants
    • Plant Resources
  • Invasive Success Hypotheses
    • Unified Framework
    • Role of Diversity >
      • How Ecosystems Maintain Diversity
      • Fluctuation Dependent Mechanisms
      • Competition-based coexistence mechanisms
      • Niche Differences
      • Species Richness
    • Enemy Release Hypothesis
    • Constitutive Defense Mechanisms
    • Evolution of Increased Competitive Ability
    • Role of Microbes
    • Indirect Defense Mechanisms
    • Novel weapons hypothesis
    • Evolutionary Shifts
    • Resource Allocation
    • Evolutionary Dynamics >
      • Pre-introduction evolutionary history
      • Sampling Effect
      • Founder Effect
      • Admixture, hybridization and polyploidization
      • Rapid Evolution
      • Epigenetics
      • Second Genomes
    • Role of Hybridization
    • Role of Native Plant Neighbors
    • Species Performance
    • Role of Herbivory
    • Evolutionary Reduced Competitive Ability
    • Summary Thoughts on Research
  • Historical Record
    • Regional Conferences
    • Timeline
  • Innovative Solutions
    • Agricultural Best Practices >
      • Ecologically based Successional Management
      • Perennial Crops, Intercropping, beneficial insects
      • Soil Solarization
      • Natural Farming
      • Permaculture
      • Organic Farming
      • Embedding Natural Habitats
      • Conservation Tillage
      • Crop Rotation
      • Water Use Practices
      • Tree Planting: Pros & Cons
    • Grazing Solutions >
      • Sheep and Goat Grazing
      • Cattle & Sheep Grazing
      • Cattle and Bison Grazing
      • Grazing and Revegetation
    • Rangeland Restoration >
      • Federal Goals for Rangelands
      • Novel Ecosystems
      • Prairie Restoration >
        • Prairie Restoration Workshop
        • Weed Prevention Areas
        • California grassland restoration
        • Selah: Bamberger Ranch Preserve
      • Sagebrush Steppe Restoration >
        • Low Nitrogen in Sagebrush Steppe
      • Revegetation with Native Plants
      • Dogs as detectors of noxious weeds
    • Nudges
  • Biological Control
    • Insects as Biocontrol >
      • Impacts of Biocontrol Agents on Non-Target Species
      • Indirect Impact of Biocontrol on Native Species
    • Challenges of Using Biocontrols >
      • DNA studies on Biocontrol Insects
      • Biocontrol takes time
    • Prioritization process for Biocontrol Programs
    • Evolutionary changes impact Biocontrol
    • Vertebrates as Biocontrol Agents
  • Herbicides: History and Impacts
    • Effectiveness of Herbicides in Agricultural Lands
    • Effectiveness of Herbicides in Rangelands
    • History of Use of Herbicides and Pesticides Prior to and During WWII
    • Herbicide use during and post-World War II >
      • 2,4-D Herbicide Use
      • 2,4-D and 2,4,5-T, post-World War II
    • Modern use of Herbicides >
      • Atrazine Herbicide
      • Dicamba Herbicide
      • Glyphosate Herbicide
      • Paraquat Dichloride
      • Picolinic acid family of herbicides >
        • Picloram (Tordon 22K) Herbicide
        • Triclopyr Herbicide
    • Herbicide Resistance in Invasive Plants >
      • Herbicide Resistant Crops
      • Controlling herbicide-resistant weeds in herbicide-resistant crops
      • Best Management Practices
    • Myth of the Silver Bullet
    • Myth of Eradication
    • Merging of Agrochemical Companies
    • Impacts of Pesticides on Environment and Human Health >
      • Pesticide Drift
      • Impacts of Pesticides on Biological Diversity
      • Impacts of Herbicides on Native Plants
      • Pesticide Impacts on Insects >
        • Butterflies: The Impacts of Herbicides
        • Monarch Butterflies: Impacts of Herbicides
      • Impacts of Pesticides on Wildlife >
        • Reptiles & Amphibians: Pesticide Impacts
      • Pesticide Residue in Foods
    • Funding for Research on Pesticides
    • Commentary on Herbicide Use
  • Interviews
    • Interviews Biocontrol >
      • Biocontrol Wyoming
      • Montana Biocontrol Interview Maggio
      • Montana Biocontrol Interview Breitenfeldt
    • California Interviews >
      • Robert Price
      • Doug Johnson
    • Colorado Interviews >
      • George Beck Interview
      • Scott Nissen Interview
    • Idaho Interviews >
      • Purple Sage Organic Farms in Idaho
    • Montana Interviews >
      • Jasmine Reimer Interview Montana
      • Organic Farms Montana Interviews
    • Texas Interviews
    • Washington Interviews >
      • Ray Willard
    • Wyoming Interviews >
      • Slade Franklin Interview
      • John Samson Interview
    • Wyoming Weed and Pest Districts >
      • Josh Shorb Interview
      • Slade Franklin Interview 2
      • Lars Baker Interview
      • Steve Brill Interview
      • George Hittle Interview
      • Peter Illoway Interview
      • Robert Jenn Interview
      • Sharon Johnson Interview
      • Larry Justesen Interview
      • Gale Lamb Interview
      • Stephen McNamee Interview
      • Allen Mooney Interview
      • Rob Orchard Interview
      • Robert Parsons Interview
      • Dick Sackett Interview
      • Comments by Delena
    • NRCS Interviews: Wyoming
  • Western Weed Control Conference 1940s Minutes
    • 1942 Conference
    • 1945 Conference
    • 1946 Conference
  • Who am I?
    • My Work
    • My Adventures
    • Contact Page
  • Road Logs
    • Colorado Road Logs
    • Idaho Road Logs
    • Montana Road Logs
    • New Mexico Road Logs
    • Texas Road Logs
    • Wyoming Road Logs
  • Bibliography