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
      • 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

Evolutionary Reduced Competitive Ability Hyphothesis

Photo: Wild Mustard, southwest Montana. © 2020 Delena Norris-Tull
​​
Evolutionary Reduced Competitive Ability (ERCA) Hypothesis: Its role 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.
 
Invasive, non-native species “do not share an evolutionary history with the community they invade, and one might expect greater allelopathic effects in such [invaded] systems” (Prati and Bossdorf, 2004). But Bossdorf, et al., 2004, have proposed that, in contrast to the enemy release hypothesis, in some species there may actually be selective pressure against non-native plants thriving in the new environment. They call this the “evolutionary reduced competitive ability” hypothesis. “If there is less [interspecific] competition in the invasive range and competitive ability involves traits that have a fitness cost, then selection might act against [those traits], thereby reducing intraspecific interactions too.”
 
The following greenhouse experiment helped them to develop this hypothesis. Garlic mustard (Alliaria petolata) is a plant native to Europe that has become an invasive and is a threat to native flora in North American forests in the northern US and southern Canada. Bossdorf, et al., 2004, collected garlic mustard seeds from eight European and eight U.S. invaded populations, to study intraspecific competition. They germinated the seeds in petri dishes filled with sterilized sand and compost. The seedlings were planted in trays with sand and potting soil. After five months, each population was replanted and grown in monoculture with the following treatments: some pots had either one plant or two plants; some were put in pairwise mixture with each of the other populations, with a total of 456 pots and 864 plants. In other words, plants were either paired with plants from their own continent or from the opposite continent. They measured the leaf lengths of the plants, and calculated a sum of squared leaf lengths, as a predictor for biomass.
 
Then the plants were grown for two years. 413 plants survived. The plants were harvested at fruit maturity. Bossdorf, et al., 2004, measured plant height and counted the number of fruits (siliques). They dried and weighed the plants and siliques to attain the biomass. “To estimate the precision of different fitness estimates [they] randomly chose 10 siliques on each plant, weighed them, and then counted and weighed the seeds.” They determined that silique biomass was a “reasonable predictor for fitness” of seed output.
 
Bossdorf, et al., 2004, found that, “Single plants produced 67% more aboveground biomass, 66% more silique biomass, and 99% more siliques than plants in pairs, suggesting that there was strong [intraspecific] competition for soil resources… Plant fitness also strongly depended on the population of origin and its interaction with density. Thus, fitness had a genetic component.” They found that “native plants were significantly taller than plants from the invasive range…. Plants of native origin growing in pairs were significantly taller (+22%) and produced significantly more siliques (+48%)… In addition, [native plants] reduced the fitness of target [American] plants with respect to silique number and silique biomass more than did [American plants].”
 
Bossdorf, et al., 2004, concluded that “under optimal, competition-free conditions there were no differences between native and invasive populations of Alliaria petiolata. When plants were competing against conspecifics, however, native populations outperformed those from the invasive range. This completely contradicts the EICA hypothesis.” “A potential caveat of this study could be that we assume no adaptive evolution… in the introduced range… We cannot exclude the possibility that local adaptation to other environment factors is responsible for the observed differences.”
 
Bossdorf, et al., 2004, stated that, “Reduced competitive ability [in the introduced range] could be the consequence of a genetic bottleneck with subsequent inbreeding depression or random changes through genetic drift…. However, we think that this explanation is rather unlikely as Alliaria has… low within-population genetic variation in both its introduced and native ranges.”
 
Bossdorf, et al., 2004, finish with, “Another explanation for reduced competitive ability in invasive populations would be directional selection. If there are fewer or weaker competitors in the [invaded habitats]…, and at the same time resource competition involves traits [in Alliaria] with a fitness cost,… then there might be selection against [those traits] in the invasive range. Furthermore, if plants in invasive populations have usually more intra- than interspecific neighbours, an Evolutionary Reduced Competitive Ability (ERCA) may increase stand-level fitness by reducing intraspecific interactions, too. It is conceivable that ERCA allows invasive populations… to use the savings not spent for resource competition in other processes that may contribute to their invasion success, such as plasticity, tolerance to herbivory, or allelopathy.”
 
Few studies have been conducted that “compared the allelopathic effects of an invasive species on competitors from the native and invaded range.” Prati and Bossdorf, 2004, carried out the following experiment. Prati and Bossdorf, 2004, tested the allelopathic response of North American and European Geum species to the root exudate from garlic mustard. The exudate has several putative allelopathic chemicals that could inhibit growth in neighboring plants.
 
Prati and Bossdorf, 2004, collected garlic mustard seeds from three different locations on each continent. They planted the mustard seeds in pots with sand and compost, in a greenhouse. They added activated carbon to half of the pots. The carbon did not inhibit the growth of garlic mustard. After a year of growth, they removed the substrate from the pots, and placed the substrate in petri dishes, in which they germinated two different species of Geum seeds. Half of the petri dishes had Geum laciniatum (a native North American species), and half had Geum urbanum (a native European species). Activated carbon was added to half the dishes.
 
They found that the garlic mustard substrate had a negative impact on the germination of co-occurring species. The two Geum species differed in their sensitivity to the allelochemicals in the substrate. They found that the carbon had a slight to moderate mitigating effect on the response to the allelochemicals, which demonstrated that the mustard plants had, in fact, exuded allelopathic chemicals to the substrate.
 
For the North American Geum laciniatum, there was no difference in the response to carbon, between substrates from either European and North American garlic mustard. Germination of the North American Geum laciniatum increased more than that of Geum urbanum, when carbon was added to the petri dishes, demonstrating that allelochemicals had moderately inhibited Geum laciniatum growth, more so than the European Geum. This result may support the novel weapons hypothesis.
 
But the European Geum urbanum results were complex. This species germinated better in substrate from the mustards from invaded North American populations. And carbon slightly decreased germination of Geum in substrate from mustard from North American populations. This suggests that the mustard in the introduced populations has reduced levels of allelochemicals. Carbon increased germination of Geum urbanum in substrate from the European mustard, suggesting that in European populations, Geum urbanum is suppressed by garlic mustard. This suggests that mustards from the European populations have higher levels of allelechemicals. These results would seem to support the evolutionary reduced competitive ability hypothesis.
 
These complex results indicate that Geum sensitivity to allelochemicals is species-specific. Prati and Bossdorf, 2004, concluded that field tests are needed to learn more about the complex interactions and the role of allelopathy between invasive and native species.

References:
  • Bossdorf, O., Prati, D., Auge, H., Schmid, B., & Knops, J. (2004). Reduced competitive ability in an invasive plant. Ecology letters, 7 (4), 346-353.
  • Prati, D., & Bossdorf, O. (2004). Allelopathic inhibition of germination by Alliaria petiolata (Brassicaceae). American Journal of Botany, 91 (2), 285-288.

Final Section on Research Hypotheses:
  • Summary Thoughts on Research on Invasive Success Hypotheses

​Links to return to the summaries of research on the success of invasive species:
creating a unified framework
the role of diversity
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
hybridization
the role of native plant neighbors
species performance
the role of herbivory
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
      • 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